Modified animal erythropoietin polypeptides and their uses

ABSTRACT

Modified animal erythropoietin polypeptides and uses thereof are provide.

FIELD OF THE INVENTION

This invention relates to feline, canine, and equine erythropoietinpolypeptides modified with at least one non-naturally-encoded aminoacid.

BACKGROUND OF THE INVENTION

The growth hormone (GH) supergene family (Bazan, F. Immunology Today 11:350-354 (1991); Mott, H. R. and Campbell, I. D. Current Opinion inStructural Biology 5: 114-121 (1995); Silvennoinen, O. and Ihle, J. N.(1996) SIGNALING BY THE HEMATOPOIETIC CYTOKINE RECEPTORS) represents aset of proteins with similar structural characteristics. While there arestill more members of the family yet to be identified, some members ofthe family include the following: growth hormone, prolactin, placentallactogen, erythropoietin (EPO), thrombopoietin (TPO), interleukin-2(IL-2), IL-3, IL-4, IL-5, IL-6, IL-7, IL-9, IL-10, IL-11, IL-12 (p35subunit), IL-13, IL-15, oncostatin M, ciliary neurotrophic factor,leukemia inhibitory factor, alpha interferon, beta interferon, gammainterferon, omega interferon, tau interferon, granulocyte-colonystimulating factor (G-CSF), granulocyte-macrophage colony stimulatingfactor (GM-CSF), macrophage colony stimulating factor (M-CSF) andcardiotrophin-1 (CT-1) (“the GH supergene family”). Members of the GHsupergene family have similar secondary and tertiary structures, despitethe fact that they generally have limited amino acid or DNA sequenceidentity. The shared structural features allow new members of the genefamily to be readily identified.

One member of the GH supergene family is feline erythropoietin (fEPO).Naturally-occurring erythropoietin (EPO) is a glycoprotein hormone ofmolecular weight 34 kilo Daltons (kDa) that is produced in the mammaliankidney and liver. EPO is a key component in erythropoiesis, inducing theproliferation and differentiation of red cell progenitors. EPO activityalso is associated with the activation of a number of erythroid-specificgenes, including globin and carbonic anhydrase. See, e.g., Bondurant etal., Mol. Cell Biol. 5:675-683 (1985); Koury et al., J. Cell. Physiol.126: 259-265 (1986).

The erythropoietin receptor (EpoR) is a member of thehematopoietic/cytokine/growth factor receptor family, which includesseveral other growth factor receptors, such as the interleukin (IL)-3,-4 and -6 receptors, the granulocyte macrophage colony-stimulatingfactor (GM-CSF) receptor as well as the prolactin and growth hormonereceptors. See, Bazan, Proc. Natl. Acad. Sci USA 87: 6934-6938 (1990).Members of the cytokine receptor family contain four conserved cysteineresidues and a tryptophan-serine-X-tryptophan-serine motif positionedjust outside the transmembrane region. The conserved sequences arethought to be involved in protein-protein interactions. See, e.g., Chibaet al., Biochim. Biophys. Res. Comm. 184: 485-490 (1992).

U.S. Pat. Nos. 5,441,868; 5,547,933; 5,618,698; and 5,621,080 describeDNA sequences encoding human EPO and the purified and isolatedpolypeptide having part or all of the primary structural conformationand the biological properties of naturally occurring EPO.

The biological effects of EPO derive from its interaction with specificcellular receptors. The interaction between EPO and extracellular domainof its receptor (EPObp) is well understood. High-resolution x-raycrystallographic data has shown that EPO has two receptor binding sitesand binds two receptor molecules sequentially using distinct sites onthe molecule. The two receptor binding sites are referred to as Site Iand Site II. Site I includes the carboxy terminal end of helix D andparts of helix A and the A-B loop, whereas Site II encompasses the aminoterminal region of helix A and a portion of helix C. Binding of EPO toits receptor occurs sequentially, with site I binding first. Site IIthen engages a second EPO receptor, resulting in receptor dimerizationand activation of the intracellular signaling pathways that lead tocellular responses to the hormone.

Recombinant human EPO is used as a therapeutic and has been approved forthe treatment of human subjects. EPO deficiency leads to anemia, forexample, which has been successfully treated by exogenous administrationof the hormone.

Anemias can be broadly divided into two categories: regenerative andnon-regenerative. Regenerative anemias tend to be caused by blood loss,or as a result of red blood cell destruction by the immune system.Non-regenerative anemias, on the other hand, are those in which the bonemarrow does not or cannot respond to the anemia. A common cause ofanemia is chronic renal failure (CRF) with most of the remaining casesbeing due to infection with the feline leukemia virus (FeLV). These twodisorders are the number 1 (FeLV) and number 2 (CRF) causes of death inpet cats. hEPO has been used in treatment of feline anemia.Unfortunately, there are concerns regarding immunogenicity when usinghEPO to treat feline anemia and around 25% to 33% of hEPO treated catsdeveloped red cell aplasia (RCA). Studies have been done, including astudy of 11 cats and 6 dogs with CRF treated with recombinant hEPO, andalthough there was some demonstrated ability to increase red blood cell(RBC) and reticulocyte countes, 5/11 cats developed anti-r-hEPO antibody(L D Cowgill, et al., J Am Vet Med Assoc. 1998 Feb. 15; 212(4):521-8). Astudy of the safety and efficacy of recombinant feline erythropoietin(rfEPO) was done with 26 test subject cats and found that although againRBC and reticulocyte counts were raised, eight out of the 26 cats (i.e.more than 30%) developed anti-r-fEPO antibodies (J E Randolph, et al, AmJ Vet Res. 2004 Oct.; 65(10):1355-66). In another study, a recombinantadeno-associated virus serotype 2 (rAAV2) vector containing felineerythropoietin cDNA was administered in a study group of 10 cats andthey found that rAAV2 antibodies were detected in all vector-treatedcats, one cat suffered pure RBC aplasia, and cats treated with lesseramounts showed no effect (M C Walker, et al., Am J Vet Res. 2005 Mar.;66(3):450-6).

Covalent attachment of the hydrophilic polymer poly(ethylene glycol),abbreviated PEG, is a method of increasing water solubility,bioavailability, increasing serum half-life, increasing therapeutichalf-life, modulating immunogenicity, modulating biological activity, orextending the circulation time of many biologically active molecules,including proteins, peptides, and particularly hydrophobic molecules.PEG has been used extensively in pharmaceuticals, on artificialimplants, and in other applications where biocompatibility, lack oftoxicity, and lack of immunogenicity are of importance. In order tomaximize the desired properties of PEG, the total molecular weight andhydration state of the PEG polymer or polymers attached to thebiologically active molecule must be sufficiently high to impart theadvantageous characteristics typically associated with PEG polymerattachment, such as increased water solubility and circulating halflife, while not adversely impacting the bioactivity of the parentmolecule.

PEG derivatives are frequently linked to biologically active moleculesthrough reactive chemical functionalities, such as lysine, cysteine andhistidine residues, the N-terminus and carbohydrate moieties. Proteinsand other molecules often have a limited number of reactive sitesavailable for polymer attachment. Often, the sites most suitable formodification via polymer attachment play a significant role in receptorbinding, and are necessary for retention of the biological activity ofthe molecule. As a result, indiscriminate attachment of polymer chainsto such reactive sites on a biologically active molecule often leads toa significant reduction or even total loss of biological activity of thepolymer-modified molecule. R. Clark et al., (1996), J. Biol. Chem.,271:21969-21977. To form conjugates having sufficient polymer molecularweight for imparting the desired advantages to a target molecule, priorart approaches have typically involved random attachment of numerouspolymer arms to the molecule, thereby increasing the risk of a reductionor even total loss in bioactivity of the parent molecule.

Reactive sites that form the loci for attachment of PEG derivatives toproteins are dictated by the protein's structure. Proteins, includingenzymes, are built of various sequences of alpha-amino acids, which havethe general structure H₂N—CHR—COOH. The alpha amino moiety (H₂N—) of oneamino acid joins to the carboxyl moiety (—COOH) of an adjacent aminoacid to form amide linkages, which can be represented as—(NH—CHR—CO)_(n)—, where the subscript “n” can equal hundreds orthousands. The fragment represented by R can contain reactive sites forprotein biological activity and for attachment of PEG derivatives.

For example, in the case of the amino acid lysine, there exists an —NH₂moiety in the epsilon position as well as in the alpha position. Theepsilon —NH₂ is free for reaction under conditions of basic pH. Much ofthe art in the field of protein derivatization with PEG has beendirected to developing PEG derivatives for attachment to the epsilon—NH₂ moiety of lysine residues present in proteins. “Polyethylene Glycoland Derivatives for Advanced PEGylation”, Nektar Molecular EngineeringCatalog, 2003, pp. 1-17. These PEG derivatives all have the commonlimitation, however, that they cannot be installed selectively among theoften numerous lysine residues present on the surfaces of proteins. Thiscan be a significant limitation in instances where a lysine residue isimportant to protein activity, existing in an enzyme active site forexample, or in cases where a lysine residue plays a role in mediatingthe interaction of the protein with other biological molecules, as inthe case of receptor binding sites.

A second and equally important complication of existing methods forprotein PEGylation is that the PEG derivatives can undergo undesiredside reactions with residues other than those desired. Histidinecontains a reactive imino moiety, represented structurally as —N(H)—,but many derivatives that react with epsilon —NH₂ can also react with—N(H)—. Similarly, the side chain of the amino acid cysteine bears afree sulfhydryl group, represented structurally as —SH. In someinstances, the PEG derivatives directed at the epsilon —NH₂ group oflysine also react with cysteine, histidine or other residues. This cancreate complex, heterogeneous mixtures of PEG-derivatized bioactivemolecules and risks destroying the activity of the bioactive moleculebeing targeted. It would be desirable to develop PEG derivatives thatpermit a chemical functional group to be introduced at a single sitewithin the protein that would then enable the selective coupling of oneor more PEG polymers to the bioactive molecule at specific sites on theprotein surface that are both well-defined and predictable.

In addition to lysine residues, considerable effort in the art has beendirected toward the development of activated PEG reagents that targetother amino acid side chains, including cysteine, histidine and theN-terminus. U.S. Pat. No. 6,610,281. “Polyethylene Glycol andDerivatives for Advanced PEGylation”, Nektar Molecular EngineeringCatalog, 2003, pp. 1-17. Cysteine residue can be introducedsite-selectively into the structure of proteins using site-directedmutagenesis and other techniques known in the art, and the resultingfree sulfhydryl moiety can be reacted with PEG derivatives that bearthiol-reactive functional groups. This approach is complicated, however,in that the introduction of a free sulfhydryl group can complicate theexpression, folding and stability of the resulting protein. Thus, itwould be desirable to have a means to introduce a chemical functionalgroup into bioactive molecules that enables the selective coupling ofone or more PEG polymers to the protein while simultaneously beingcompatible with (i.e., not engaging in undesired side reactions with)sulfhydryls and other chemical functional groups typically found inproteins.

As can be seen from a sampling of the art, many of these derivativesthat have been developed for attachment to the side chains of proteins,in particular, the —NH₂ moiety on the lysine amino acid side chain andthe —SH moiety on the cysteine side chain, have proven problematic intheir synthesis and use. Some form unstable linkages with the proteinthat are subject to hydrolysis and therefore decompose, degrade, or areotherwise unstable in aqueous environments, such as in the blood stream.Some form more stable linkages, but are subject to hydrolysis before thelinkage is formed, which means that the reactive group on the PEGderivative may be inactivated before the protein can be attached. Someare somewhat toxic and are therefore less suitable for use in vivo. Someare too slow to react to be practically useful. Some result in a loss ofprotein activity by attaching to sites responsible for the protein'sactivity. Some are not specific in the sites to which they will attach,which can also result in a loss of desirable activity and in a lack ofreproducibility of results. In order to overcome the challengesassociated with modifying proteins with poly(ethylene glycol) moieties,PEG derivatives have been developed that are more stable (e.g., U.S.Pat. No. 6,602,498) or that react selectively with thiol moieties onmolecules and surfaces (e.g., U.S. Pat. No. 6,610,281). There is clearlya need in the art for PEG derivatives that are chemically inert inphysiological environments until called upon to react selectively toform stable chemical bonds.

Recently, an entirely new technology in the protein sciences has beenreported, which promises to overcome many of the limitations associatedwith site-specific modifications of proteins. Specifically, newcomponents have been added to the protein biosynthetic machinery of theprokaryote Escherichia coil (E. coli) (e.g., L. Wang, et al., (2001),Science 292:498-500) and the eukaryote Saccharomyces cerevisiae (S.cerevisiae) (e.g., J. Chin et al., Science 301:964-7 (2003)), which hasenabled the incorporation of non-genetically encoded amino acids toproteins in vivo. A number of new amino acids with novel chemical,physical or biological properties, including photoaffinity labels andphotoisomerizable amino acids, keto amino acids, and glycosylated aminoacids have been incorporated efficiently and with high fidelity intoproteins in E. coli and in yeast in response to the amber codon, TAG,using this methodology. See, e.g., J. W. Chin et al., (2002), Journal ofthe American Chemical Society 124:9026-9027; J. W. Chin, & P. G.Schultz, (2002), ChemBioChem 11:1135-1137; J. W. Chin, et al., (2002),PNAS United States of America 99:11020-11024: and, L. Wang, & P. G.Schultz, (2002), Chem. Comm., 1-10. These studies have demonstrated thatit is possible to selectively and routinely introduce chemicalfunctional groups, such as alkyne groups and azide moieties, that arenot found in proteins, that are chemically inert to all of thefunctional groups found in the 20 common, genetically-encoded aminoacids and that may be used to react efficiently and selectively to formstable covalent linkages.

The ability to incorporate non-genetically encoded amino acids intoproteins permits the introduction of chemical functional groups thatcould provide valuable alternatives to the naturally-occurringfunctional groups, such as the epsilon —NH₂ of lysine, the sulfhydryl—SH of cysteine, the imino group of histidine, etc. Certain chemicalfunctional groups are known to be inert to the functional groups foundin the 20 common, genetically-encoded amino acids but react cleanly andefficiently to form stable linkages. Azide and acetylene groups, forexample, are known in the art to undergo a Huisgen [3+2] cycloadditionreaction in aqueous conditions in the presence of a catalytic amount ofcopper. See, e.g., Tornoe, et al., (2002) Org. Chem. 67:3057-3064; and,Rostovtsev, et al., (2002) Angew. Chem. Int. Ed. 41:2596-2599. Byintroducing an azide moiety into a protein structure, for example, oneis able to incorporate a functional group that is chemically inert toamines, sulfhydryls, carboxylic acids, hydroxyl groups found inproteins, but that also reacts smoothly and efficiently with anacetylene moiety to form a cycloaddition product. Importantly, in theabsence of the acetylene moiety, the azide remains chemically inert andunreactive in the presence of other protein side chains and underphysiological conditions.

The present invention addresses, among other things, problems associatedwith the activity and production of EPO, and also addresses theproduction of a hEPO polypeptide with improved biological orpharmacological properties, such as improved therapeutic half-life.

BRIEF SUMMARY OF THE INVENTION

This invention provides fEPO polypeptides comprising a non-naturallyencoded amino acid.

In some embodiments, the fEPO polypeptide is linked to a second fEPOpolypeptide.

In some embodiments, the non-naturally encoded amino acid is linked to awater soluble polymer. In some embodiments, the water soluble polymercomprises a poly(ethylene glycol) moiety. In some embodiments, thepoly(ethylene glycol) molecule is a bifunctional polymer. In someembodiments, the bifunctional polymer is linked to a second polypeptide.In some embodiments, the second polypeptide is a fEPO polypeptide.

In some embodiments, the fEPO polypeptide comprises at least two aminoacids linked to a water soluble polymer comprising a poly(ethyleneglycol) moiety. In some embodiments, at least one amino acid is anon-naturally encoded amino acid.

In some embodiments, the one or more non-naturally encoded amino acidsare incorporated at any position in one or more of the following regionscorresponding to secondary structures in fEPO as follows: 1-7(N-terminus), 8-26 (A helix), 27-54 (region between A helix and B helix)55-83 (B helix), 84-89 (region between B helix and C helix), 90-112 (Chelix), 113-137 (region between C helix and D helix), 138-161 (D helix),162-166 (C-terminus), 39-41 (beta sheet 1), 133-135 (beta sheet 2),47-52 (mini B loop), 114-121 (mini C loop), 34-38 (loop between A helixand the anti-parallel beta1 sheet), 51-57 (C-terminal end of the B′helix, loop between B′ helix and B helix and N-terminal end of theB-helix), 82-92 (region between the B helix and the C helix), and120-133 (region between the C′ helix and anti-parallel beta sheet 2). Insome embodiments, the one or more non-naturally encoded amino acids areincorporated in one of the following positions in fEPO: 1, 2, 3, 4, 5,6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24,25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42,43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60,61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78,79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96,97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111,112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125,126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139,140, 141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151, 152, 153,154, 155, 156, 157, 158, 159, 160, 161, 162, 163, 164, 165 and 166. Insome embodiments, the one or more non-naturally encoded amino acids areincorporated in one of the following positions in fEPO: 1, 2, 3, 4, 5,6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 19, 20, 21, 22, 23, 24, 25,26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43,44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61,62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79,80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97,98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112,113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126,127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 140,141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151, 152, 153, 154,155, 156, 157, 158, 159, 160, 161, 162, 163, 164, 165 and 166. In someembodiments, the one or more non-naturally encoded amino acids areincorporated in one of the following positions in fEPO: 1, 2, 3, 4, 5,6, 17, 21, 24, 27, 28, 30, 31, 32, 34, 35, 36, 37, 38, 40, 50, 51, 52,53, 54, 55, 56, 57, 58, 68, 72, 76, 80, 82, 83, 84, 85, 86, 87, 88, 89,90, 91, 92, 113, 116, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128,129, 130, 131, 132, 133, 134, 136, 162, 163, 164, 165 and 166. In someembodiments, the one or more non-naturally encoded amino acids areincorporated in one of the following positions in fEPO: 1, 2, 3, 4, 5,6, 17, 18, 21, 24, 27, 28, 30, 31, 32, 34, 35, 36, 37, 38, 40, 50, 51,52, 53, 54, 55, 56, 57, 58, 68, 72, 76, 80, 82, 83, 84, 85, 86, 87, 88,89, 90, 91, 92, 113, 116, 119, 120, 121, 122, 123, 124, 125, 126, 127,128, 129, 130, 131, 132, 133, 134, 136, 162, 163, 164, 165 and 166. Insome embodiments, the fEPO polypeptides of the invention comprise one ormore non-naturally occurring amino acids at one or more of the followingpositions: 21, 24, 27, 28, 30, 31, 34, 36, 37, 38, 40, 55, 68, 72, 76,83, 85, 86, 87, 89, 113, 116, 119, 120, 121, 123, 124, 125, 126, 127,128, 129, 130, 136, and 162. In some embodiments, the non-naturallyoccurring amino acid at these or other positions is linked to a watersoluble molecule, including but not limited to positions 21, 24, 38, 83,85, 116, and 119. In some embodiments, the fEPO polypeptides of theinvention comprise one or more non-naturally occurring amino acids atone or more of the following positions: 18, 53, 58, 116, 121, 89, 94,72, 77, 86, 91, 31, 36, 132, 137, 163, 168, 120, 125, 55, and 60. Insome embodiments, the fEPO polypeptides of the invention comprise one ormore non-naturally occurring amino acids at one or more of the followingpositions: 53, 58, 116, 121, 89, 94, 72, 77, 86, 91, 31, 36, 132, 137,163, 168, 120, 125, 55, and 60. In some embodiments, the fEPOpolypeptides of the invention comprise one or more non-naturallyoccurring amino acids at one or more of the following positions: 18, 53,58, 116, 121, 89, 94, 72, 77, 86, 91, 31, 36, 132, 137, 163, 168, 120,125, 55, and 60. In some embodiments, the non-naturally occurring aminoacid at these or other positions is linked to a water soluble molecule,including but not limited to positions 53, 58, 116, 121, 89, 94, 72, 77,86, 91, 31, 36, 132, 137, 163, 168, 120, 125, 55, and 60. In someembodiments, the fEPO polypeptides of the invention comprise one or morenon-naturally occurring amino acids at one or more of the followingpositions: 123, 124, 125, 126, 127, 128, 129, and 130. In someembodiments, the non-naturally occurring amino acid at these or otherpositions is linked to a water soluble molecule, including but notlimited to positions 123, 124, 125, 126, 127, 128, 129, and 130.

In some embodiments, the fEPO polypeptide comprises a substitution,addition or deletion that increases affinity of the fEPO polypeptide foran erythropoietin receptor. In some embodiments, the fEPO polypeptidecomprises a substitution, addition, or deletion that increases thestability of the fEPO polypeptide. In some embodiments, the fEPOpolypeptide comprises a substitution, addition, or deletion thatincreases the aqueous solubility of the fEPO polypeptide. In someembodiments, the fEPO polypeptide comprises a substitution, addition, ordeletion that increases the solubility of the fEPO polypeptide producedin a host cell. In some embodiments, the fEPO polypeptide comprises asubstitution of an amino acid selected from the group consisting of, butnot limited to, N24, N36, N38, Q58, Q65, N83, Q86, G113, Q115, and S126and combination thereof in SEQ ID NO: 2. In some embodiments, the fEPOpolypeptide comprises a substitution of an amino acid selected from thegroup consisting of, but not limited to, N24, N36, N38, Q58, Q65, N83,Q86, G113, Q115, and S126 and combination thereof in SEQ ID NO: 4.

In some embodiments the amino acid substitutions in the fEPO polypeptidemay be with naturally occurring or non-naturally occurring amino acids,provided that at least one substitution is with a non-naturally encodedamino acid.

In some embodiments, the non-naturally encoded amino acid comprises acarbonyl group, an acetyl group, an aminooxy group, a hydrazine group, ahydrazide group, a semicarbazide group, an azide group, or an alkynegroup.

In some embodiments, the non-naturally encoded amino acid comprises acarbonyl group. In some embodiments, the non-naturally encoded aminoacid has the structure:

wherein n is 0-10; R₁ is an alkyl, aryl, substituted alkyl, orsubstituted aryl; R₂ is H, an alkyl, aryl, substituted alkyl, andsubstituted aryl; and R₃ is H, an amino acid, a polypeptide, or an aminoterminus modification group, and R₄ is H, an amino acid, a polypeptide,or a carboxy terminus modification group.

In some embodiments, the non-naturally encoded amino acid comprises anaminooxy group. In some embodiments, the non-naturally encoded aminoacid comprises a hydrazide group. In some embodiments, the non-naturallyencoded amino acid comprises a hydrazine group. In some embodiments, thenon-naturally encoded amino acid residue comprises a semicarbazidegroup.

In some embodiments, the non-naturally encoded amino acid residuecomprises an azide group. In some embodiments, the non-naturally encodedamino acid has the structure:

wherein n is 0-10; R₁ is an alkyl, aryl, substituted alkyl, substitutedaryl or not present; X is O, N, S or not present; m is 0-10; R₂ is H, anamino acid, a polypeptide, or an amino terminus modification group, andR₃ is H, an amino acid, a polypeptide, or a carboxy terminusmodification group.

In some embodiments, the non-naturally encoded amino acid comprises analkyne group. In some embodiments, the non-naturally encoded amino acidhas the structure:

wherein n is 0-10; R1 is an alkyl, aryl, substituted alkyl, orsubstituted aryl; X is O, N, S or not present; m is 0-10, R₂ is H, anamino acid, a polypeptide, or an amino terminus modification group, andR₃ is H, an amino acid, a polypeptide, or a carboxy terminusmodification group.

In some embodiments, the polypeptide is an erythropoietin agonist,partial agonist, antagonist, partial antagonist, or inverse agonist. Insome embodiments, the erythropoietin agonist, partial agonist,antagonist, partial antagonist, or inverse agonist comprises anon-naturally encoded amino acid is linked to a water soluble polymer.In some embodiments, the water soluble polymer comprises a poly(ethyleneglycol) moiety. In some embodiments, the non-naturally encoded aminoacid linked to a water soluble polymer is present within the Site 2region (the region of the protein encompassing the AC helical-bundleface) of fEPO. In some embodiments, the fEPO polypeptide comprising anon-naturally encoded amino acid linked to a water soluble polymerprevents dimerization of the fEPO receptor by preventing the fEPOantagonist from binding to a second fEPO receptor molecule. In someembodiments, an amino acid other than leucine is substituted for L108 inSEQ ID NO: 2. In some embodiments, arginine or lysine is substituted forL108 in SEQ ID NO: 2. In some embodiments, a non-naturally encoded aminoacid is substituted for L108 in SEQ ID NO: 2.

The present invention also provides isolated nucleic acids comprising apolynucleotide that hybridizes under stringent conditions to SEQ ID NO:24, 25, 26, or 27, wherein the polynucleotide comprises at least oneselector codon. In some embodiments, the selector codon is selected fromthe group consisting of an amber codon, ochre codon, opal codon, aunique codon, a rare codon, and a four-base codon.

The present invention also provides methods of making a fEPO polypeptidelinked to a water soluble polymer. In some embodiments, the methodcomprises contacting an isolated fEPO polypeptide comprising anon-naturally encoded amino acid with a water soluble polymer comprisinga moiety that reacts with the non-naturally encoded amino acid. In someembodiments, the non-naturally encoded amino acid incorporated into fEPOis reactive toward a water soluble polymer that is otherwise unreactivetoward any of the 20 common amino acids.

In some embodiments, the fEPO polypeptide linked to the water solublepolymer is made by reacting a fEPO polypeptide comprising acarbonyl-containing amino acid with a poly(ethylene glycol) moleculecomprising an aminooxy, a hydroxylamine, hydrazine, hydrazide orsemicarbazide group. In some embodiments, the aminooxy, hydroxylamine,hydrazine, hydrazide or semicarbazide group is linked to thepoly(ethylene glycol) molecule through an amide linkage.

In some embodiments, the fEPO polypeptide linked to the water solublepolymer is made by reacting a poly(ethylene glycol) molecule comprisinga carbonyl group with a polypeptide comprising a non-naturally encodedamino acid that comprises a hydroxylamine, hydrazide or semicarbazidegroup.

In some embodiments, the fEPO polypeptide linked to the water solublepolymer is made by reacting a fEPO polypeptide comprising analkyne-containing amino acid with a poly(ethylene glycol) moleculecomprising an azide moiety. In some embodiments, the azide or alkynegroup is linked to the poly(ethylene glycol) molecule through an amidelinkage.

In some embodiments, the fEPO polypeptide linked to the water solublepolymer is made by reacting a fEPO polypeptide comprising anazide-containing amino acid with a poly(ethylene glycol) moleculecomprising an alkyne moiety. In some embodiments, the azide or alkynegroup is linked to the poly(ethylene glycol) molecule through an amidelinkage.

In some embodiments, the poly(ethylene glycol) molecule has a molecularweight of between about 1 and about 100 kDa. In some embodiments, thepoly(ethylene glycol) molecule has a molecular weight of between 1 kDaand 50 kDa.

In some embodiments, the poly(ethylene glycol) molecule is a branchedpolymer. In some embodiments, each branch of the poly(ethylene glycol)branched polymer has a molecular weight of between 1 kDa and 100 kDa, orbetween 1 kDa and 50 kDa.

In some embodiments, the water soluble polymer linked to fEPO comprisesa polyalkylene glycol moiety. In some embodiments, the non-naturallyencoded amino acid residue incorporated into fEPO comprises a carbonylgroup, an acetyl group, an aminooxy group, a hydrazide group, asemicarbazide group, an azide group, or an alkyne group. In someembodiments, the non-naturally encoded amino acid residue incorporatedinto fEPO comprises a carbonyl moiety and the water soluble polymercomprises an aminooxy, a hydroxylamine, hydrazide or semicarbazidemoiety. In some embodiments, the non-naturally encoded amino acidresidue incorporated into fEPO comprises an alkyne moiety and the watersoluble polymer comprises an azide moiety. In some embodiments, thenon-naturally encoded amino acid residue incorporated into fEPOcomprises an azide moiety and the water soluble polymer comprises analkyne moiety.

The present invention also provides compositions comprising a fEPOpolypeptide comprising a non-naturally-encoded amino acid and apharmaceutically acceptable carrier. In some embodiments, thenon-naturally encoded amino acid is linked to a water soluble polymer.

The present invention also provides cells comprising a polynucleotideencoding the fEPO polypeptide comprising a selector codon. In someembodiments, the cells comprise an orthogonal RNA synthetase and/or anorthogonal tRNA for substituting a non-naturally encoded amino acid intothe fEPO polypeptide.

The present invention also provides methods of making a fEPO polypeptidecomprising a non-naturally encoded amino acid. In some embodiments, themethods comprise culturing cells comprising a polynucleotide orpolynucleotides encoding a fEPO polypeptide, an orthogonal RNAsynthetase and an orthogonal tRNA under conditions to permit expressionof the fEPO polypeptide; and purifying the fEPO polypeptide from thecells and/or culture medium.

The present invention also provides methods of increasing therapeutichalf-life, serum half-life or circulation time of fEPO. In someembodiments, the methods comprise substituting a non-naturally encodedamino acid for any one or more amino acids in naturally occurring fEPOand/or linking the fEPO polypeptide to a water soluble polymer.

The present invention also provides methods of treating a patient inneed of such treatment with an effective amount of a fEPO molecule ofthe present invention. In some embodiments, the methods compriseadministering to the patient a therapeutically-effective amount of apharmaceutical composition comprising a fEPO polypeptide comprising anon-naturally-encoded amino acid and a pharmaceutically acceptablecarrier. In some embodiments, the non-naturally encoded amino acid islinked to a water soluble polymer.

The present invention also provides fEPO polypeptides comprising asequence shown in SEQ ID NO: 1, 2, 3, or 4, except that at least oneamino acid is substituted by a non-naturally encoded amino acid. In someembodiments, the non-naturally encoded amino acid is linked to a watersoluble polymer. In some embodiments, the water soluble polymercomprises a poly(ethylene glycol) moiety. In some embodiments, thenon-naturally encoded amino acid is substituted at a position selectedfrom the group consisting of residues including but not limited to 1-6,21-40, 68-89, 116-136, 162-166 from SEQ ID NO: 2, or SEQ ID NO: 4, orthe corresponding amino acid position of SEQ ID NO:1 or SEQ ID NO: 3. Insome embodiments, the non-naturally encoded amino acid comprises acarbonyl group, an aminooxy group, a hydrazide group, a hydrazine group,a semicarbazide group, an azide group, or an alkyne group.

The present invention also provides pharmaceutical compositionscomprising a pharmaceutically acceptable carrier and a fEPO polypeptidecomprising the sequence shown in SEQ ID NO: 1, 2, 3, or 4, wherein atleast one amino acid is substituted by a non-naturally encoded aminoacid. The present invention also provides pharmaceutical compositionscomprising a pharmaceutically acceptable carrier and a fEPO polypeptidecomprising the sequence shown in SEQ ID NO: 2 or 4, wherein at least oneamino acid is substituted by a non-naturally encoded amino acid. In someembodiments, the non-naturally encoded amino acid comprises a saccharidemoiety. In some embodiments, the water soluble polymer is linked to thepolypeptide via a saccharide moiety.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1—A diagram of the sequence alignment of human and felineerythropoietin.

FIG. 2—A diagram highlighting the difference between the two sequencesdeposited in Genbank (Genbank accession No. U00685 and Genbank accessionNo. L10606), the consensus sequence.

FIG. 3—A diagram of the general structure for the four helical bundleprotein erythropoietin (EPO) is shown with high and low affinityreceptors.

FIG. 4—A diagram of an alternate view of the general structure for thefour helical bundle protein erythropoietin (EPO) is shown with high andlow affinity receptors.

FIG. 5—A diagram showing some selected sites for incorporation ofnon-naturally encoded amino acids.

FIG. 6—A diagram showing a top view of some selected sites forincorporation of non-naturally encoded amino acids.

FIG. 7—A diagram showing a side view of some selected sites forincorporation of non-naturally encoded amino acids, and highlightingwhich of those sites are close to glycosylation sites.

FIG. 8—A chart of some selected sites for incorporation of non-naturallyencoded amino acids, the naturally occurring amino acid and the aminoacid position from SEQ ID NO: 2 and SEQ ID NO: 4 and the average Cx forthose sites.

FIG. 9—A chart of some selected sites for incorporation of non-naturallyencoded amino acids, the naturally occurring amino acid and the aminoacid position from SEQ ID NO: 2 and SEQ ID NO: 4 and the average Cx forthose sites.

FIG. 10 a—The optical density at 450 nm graphed against theconcentration of formulation buffer.

FIG. 10 b—The optical density at 450 nm graphed against theconcentration of endotoxin.

FIG. 11—A diagram of the TF-1 proliferation assay.

FIG. 12—A diagram of fEPO receptors homodimerizing upon ligand binding.

FIG. 13—The OD at 450 nm plotted against increasing concentrations offEPO showing a bell-shaped dose response curve.

FIG. 14—A displaying different seeding densities of TF-1 cells. Thisgraph shows that, given, for example, the JAK-STAT signal transductionpathway, for optimal activity in response to fEPO the ratio of betweenfEPO and fEPO receptor is 1:2.

FIG. 15—A graph of experimental results determining whether cellstarvation would synchronize cellular division and result in a greaterdynamic range—the results showed that this was not particularlyadvantageous.

FIG. 16—A graph of conditions used for the TF-1 assay with seedingdensity of 20,000, an incubation time of 72 hours, fEPO startingconcentration of 500 ng/ml and dilution 2.5×.

FIG. 17—A chart measuring the assay robustness, providing data on thecell passage number, EC50, OD's and dynamic ranges.

FIG. 18—A chart and graph of the TF-1 assay performance with wild typefEPO and formulation buffer.

FIG. 19—A graph comparing the assay performance between wild type EPOsfor human and feline.

FIG. 20—A graph of measured ODs against varying concentrations of CHOconditioned and unconditioned media with wild type fEPO as control.

FIG. 21—A graph comparing wild type fEPO, CHO/PEI+1.25 ng/mL fEPO andCHO/PEI alone in decreasing concentrations and their measured ODs.

FIG. 22—A chart and graphs of the relative activity of fEPO variantswith an incorporated non-natural amino acid, pAF, as compared to wildtype fEPO.

FIG. 23—A bar graph of several fEPO variants with incorporated pAF atspecified sites and each of ther ED50 ng/mL measurements.

FIG. 24—A graph of E72 fEPO variant stored at four degrees and minuseighty degrees over five weeks, as compared to wild type fEPO, and theirODs.

FIG. 25—A schematic drawing of the Lucy F vector and the situs of thetRNAs, gene of interest transcriptional element, and the tRNAsynthetase.

FIG. 26—A schematic drawing of the Irwin vector and the situs of thetRNAs, gene of interest transcriptional element, and the tRNAsynthetase.

FIG. 27—A schematic drawing of the suppression expression construct NatL BB-Opti FEPO in Lucy F for feline erythropoietin.

FIG. 28—A schematic drawing of the suppression expression construct NatL BB-Opti FEPO in Irwin for feline erythropoietin.

FIG. 29—A schematic drawing depicting a suppression expression constructaccording to the invention encoding a generic antibody with light andheavy chain genes

FIG. 30—A bar graph showing the suppression levels of fEPO variants inthe presence of pAF measured by ELISA (OD-50).

FIG. 31—Shows a comparison of PEGylated fEPO migration by SDS-PAGE.Lanes 1-3: 20 kDa PEG reactions with fEPO R53 pAF variant. Lane 1: R53,8 μg fEPO load, no PEG. Lane 2: R53 PEGylation, 2 μg fEPO load. Lane 3:R53 PEGylation, 8 μg fEPO load. Lanes 4-6: 30 kDa PEG reactions withfEPO P129 pAF variant. Lane 4: P129, 8 μg fEPO load, no PEG. Lane 5:P129 PEGylation, 2 μg fEPO load. Lane 6: P129 PEGylation, 8 μg fEPOload. Lanes 7-9: 40 kDa PEG reactions with fEPO Y49 pAF variant. Lane 7:Y49, 8 μg fEPO load, no PEG. Lane 9: Y49 PEGylation, 8 μg fEPO load.Lane 9: Y49 PEGylation, 2 μg fEPO load. The horizontal arrow at 38 kDaindicates the location of unPEGylated fEPO migration. The boxedrectangle indicates the region of PEGylated fEPO migration.

FIG. 32—An SDS-PAGE gel showing the PEGylation reactions (30 kDa) forfEPO D55 and P129 pAF variants, showing these two PEGylated variants.Lane 1: D55, no PEG. Lane 2: D55 PEGylation Lane 3: wild-type fEPO, noincubation. Lane 4: P129, 8 μg fEPO load, no PEG. Lane 5: P129PEGylation, 2 μg fEPO load. Lane 6: P129 PEGylation, 8 μg fEPO load. Thehorizontal arrow at 38 kDa indicates the location of unPEGylated fEPOmigration. The boxed rectangle indicates the region of PEGylated fEPOmigration.

FIG. 33—An SDS-PAGE gel showing the successful pegylation reaction (30kDa) for fEPO A1 pAF variant. Lane 1 shows wild-type fEPO, 8 μg load, noincubation and lane 2: shows PEGylated A1.

FIG. 34—A comparison between the cEPO (SEQ ID NO: 31) and fEPO (SEQ IDNO: 4) amino acid sequences showing the 94% homology between the two.

FIG. 35—A comparison between the eEPO (SEQ ID NO: 33) and fEPO (SEQ IDNO: 4) amino acid sequences showing the 94% homology between the two.

FIG. 36—A graph showing the effects of the various treatments uponhematocrits and red blood cells (RBC) from the experiment run in example32.

DEFINITIONS

It is to be understood that this invention is not limited to theparticular methodology, protocols, cell lines, constructs, and reagentsdescribed herein and as such may vary. It is also to be understood thatthe terminology used herein is for the purpose of describing particularembodiments only, and is not intended to limit the scope of the presentinvention, which will be limited only by the appended claims.

As used herein and in the appended claims, the singular forms “a,” “an,”and “the” include plural reference unless the context clearly indicatesotherwise. Thus, for example, reference to a “fEPO” is a reference toone or more such proteins and includes equivalents thereof known tothose skilled in the art, and so forth.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood to one of ordinary skill inthe art to which this invention belongs. Although any methods, devices,and materials similar or equivalent to those described herein can beused in the practice or testing of the invention, the preferred methods,devices and materials are now described.

All publications and patents mentioned herein are incorporated herein byreference for the purpose of describing and disclosing, for example, theconstructs and methodologies that are described in the publications,which might be used in connection with the presently describedinvention. The publications discussed herein are provided solely fortheir disclosure prior to the filing date of the present application.Nothing herein is to be construed as an admission that the inventors arenot entitled to antedate such disclosure by virtue of prior invention orfor any other reason.

The term “substantially purified” refers to fEPO that may besubstantially or essentially free of components that normally accompanyor interact with the protein as found in its naturally occurringenvironment, i.e. a native cell, or host cell in the case ofrecombinantly produced fEPO. fEPO that may be substantially free ofcellular material includes preparations of protein having less thanabout 30%, less than about 25%, less than about 20%, less than about15%, less than about 10%, less than about 5%, less than about 4%, lessthan about 3%, less than about 2%, or less than about 1% (by dry weight)of contaminating protein. When the fEPO or variant thereof isrecombinantly produced by the host cells, the protein may be present atabout 30%, about 25%, about 20%, about 15%, about 10%, about 5%, about4%, about 3%, about 2%, or about 1% or less of the dry weight of thecells. When the fEPO or variant thereof is recombinantly produced by thehost cells, the protein may be present in the culture medium at about 5g/L, about 4 g/L, about 3 g/L, about 2 g/L, about 1 g/L, about 750 mg/L,about 500 mg/L, about 250 mg/L, about 100 mg/L, about 50 mg/L, about 10mg/L, or about 1 mg/L or less of the dry weight of the cells. Thus,“substantially purified” fEPO as produced by the methods of the presentinvention may have a purity level of at least about 30%, at least about35%, at least about 40%, at least about 45%, at least about 50%, atleast about 55%, at least about 60%, at least about 65%, at least about70%, specifically, a purity level of at least about 75%, 80%, 85%, andmore specifically, a purity level of at least about 90%, a purity levelof at least about 95%, a purity level of at least about 99% or greateras determined by appropriate methods such as SDS/PAGE analysis, RP-HPLC,SEC, and capillary electrophoresis.

A “recombinant host cell” or “host cell” refers to a cell that includesan exogenous polynucleotide, regardless of the method used forinsertion, for example, direct uptake, transduction, f-mating, or othermethods known in the art to create recombinant host cells. The exogenouspolynucleotide may be maintained as a nonintegrated vector, for example,a plasmid, or alternatively, may be integrated into the host genome.

As used herein, the term “medium” or “media” includes any culturemedium, solution, solid, semi-solid, or rigid support that may supportor contain any host cell, including bacterial host cells, yeast hostcells, insect host cells, plant host cells, eukaryotic host cells,mammalian host cells, CHO cells or E. coli, and cell contents. Thus, theterm may encompass medium in which the host cell has been grown, e.g.,medium into which the fEPO has been secreted, including medium eitherbefore or after a proliferation step. The teen also may encompassbuffers or reagents that contain host cell lysates, such as in the casewhere fEPO is produced intracellularly and the host cells are lysed ordisrupted to release the fEPO.

As used herein, “IRES” or an internal ribosome entry site, is known tothose skilled in the art. IRES is a region of a nucleic acid moleculee.g., an mRNA molecule, that allows internal ribosome entry/bindingsufficient to initiate translation in an assay for cap-independenttranslation, such as the bicistronic reporter assay described in U.S.Pat. No. 6,715,821. The presence of an IRES within an mRNA moleculeallows cap-independent translation of a linked protein-encoding sequencethat otherwise would not be translated. IRES's were first identified inpicornaviruses, and are considered the paradigm for cap-independenttranslation. The 5′ UTRS of all picornaviruses are long and mediatetranslational initiation by directly recruiting and binding ribosomes,thereby circumventing the initial cap-binding step.

IRES elements are frequently found in viral mRNAS, and are rarely foundin non-viral mRNAs. To date, the non-viral mRNAS shown to containfunctional IRES elements in their respective 5′ UTRS include thoseencoding immunoglobulin heavy chain binding protein (BIP) (Macejak, D.J. et al., Nature 353:90-94 (1991)); Drosophila Antennapedia (Oh, S. K.et al., Genes Dev. 6:1643-53 (1992)); and Ultrabithoran (Ye, X. et al.,Mol. Cell. Biol. 17:1714-21 (1997)); fibroblast growth factor 2 (Vagneret al., Mol. Cell. Biol. 15:35-47 (1915); initiation factor (Gan et al.,J. Biol. Chem. 273:5006-12 (1992)); protein-oncogene c-myc (Nambru etal., J. Biol. Chem. 272:32061-6 (1995)); Stonely M. Oncogene 16:423-8(1998)); Vascular endothelial growth factor (VEGF) (Stein J. et al.,Mol. Cell. Biol. 18:3112-9 (1998)). Cellular IRES elements have noobvious sequence or structural similarity to IRES sequences or to eachother and therefore are identified using translational assays. Anotherknown IRES is the XIAP IRES disclosed in U.S. Pat. No. 6,171,821,incorporated by reference in its entirety herein.

“Reducing agent,” as used herein with respect to protein refolding, isdefined as any compound or material which maintains sulfhydryl groups inthe reduced state and reduces intra- or intermolecular disulfide bonds.Suitable reducing agents include, but are not limited to, dithiothreitol(DTT), 2-mercaptoethanol, dithioerythritol, cysteine, cysteamine(2-aminoethanethiol), and reduced glutathione. It is readily apparent tothose of ordinary skill in the art that a wide variety of reducingagents are suitable for use in the methods of the present invention.

“Oxidizing agent,” as used hereinwith respect to protein refolding, isdefined as any compound or material which is capable of removing anelectron from a compound being oxidized. Suitable oxidizing agentsinclude, but are not limited to, oxidized glutathione, cystine,cystamine, oxidized dithiothreitol, oxidized erythreitol, and oxygen. Itis readily apparent to those of ordinary skill in the art that a widevariety of oxidizing agents are suitable for use in the methods of thepresent invention.

“Denaturing agent” or “denaturant,” as used herein, is defined as anycompound or material which will cause a reversible unfolding of aprotein. The strength of a denaturing agent or denaturant will bedetermined both by the properties and the concentration of theparticular denaturing agent or denaturant. Suitable denaturing agents ordenaturants may be chaotropes, detergents, organic, water misciblesolvents, phospholipids, or a combination of two or more such agents.Suitable chaotropes include, but are not limited to, urea, guanidine,and sodium thiocyanate. Useful detergents may include, but are notlimited to, strong detergents such as sodium dodecyl sulfate, orpolyoxyethylene ethers (e.g. Tween or Triton detergents), Sarkosyl, mildnon-ionic detergents (e.g., digitonin), mild cationic detergents such asN→2,3-(Dioleyoxy)-propyl-N,N,N-trimethylammonium, mild ionic detergents(e.g. sodium cholate or sodium deoxycholate) or zwitterionic detergentsincluding, but not limited to, sulfobetaines (Zwittergent),3-(3-chlolamidopropyl)dimethylammonio-1-propane sulfate (CHAPS), and3-(3-chlolamidopropyl)dimethylammonio-2-hydroxy-1-propane sulfonate(CHAPSO). Organic, water miscible solvents such as acetonitrile, loweralkanols (especially C₂-C₄ alkanols such as ethanol or isopropanol), orlower alkandiols (especially C₂-C₄ alkandiols such as ethylene-glycol)may be used as denaturants. Phospholipids useful in the presentinvention may be naturally occurring phospholipids such asphosphatidylethanolamine, phosphatidylcholine, phosphatidylserine, andphosphatidylinositol or synthetic phospholipid derivatives or variantssuch as dihexanoylphosphatidylcholine or diheptanoylphosphatidylcholine.

“Refolding,” as used herein describes any process, reaction or methodwhich transforms disulfide bond containing polypeptides from animproperly folded or unfolded state to a native or properly foldedconformation with respect to disulfide bonds.

“Cofolding,” as used herein, refers specifically to refolding processes,reactions, or methods which employ at least two polypeptides whichinteract with each other and result in the transformation of unfolded orimproperly folded polypeptides to native, properly folded polypeptides.

As used herein, “erythropoietin” or “EPO” shall include thosepolypeptides and proteins that have at least one biological activity offeline erythropoietin (fEPO), as well as erythropoietin analogs,erythropoietin isoforms (such as those described in U.S. Pat. No.5,856,298 which is incorporated by reference herein), erythropoietinmimetics (such as those described in U.S. Pat. No. 6,310,078 which isincorporated by reference herein), erythropoietin fragments, hybriderythropoietin proteins, fusion proteins oligomers and multimers,homologues, glycosylation pattern variants, and muteins, regardless ofthe biological activity of same, and further regardless of the method ofsynthesis or manufacture thereof including, but not limited to,recombinant (whether produced from cDNA or genomic DNA), synthetic,transgenic, and gene activated methods. Specific examples oferythropoietin include, but are not limited to, epoetin alfa (such asthose described in U.S. Pat. No. 4,667,016; 4,703,008; 5,441,868;5,547,933; 5,618,698; 5,621,080; 5,756,349; and 5,955,422 which areincorporated by reference herein), darbepoetin alfa (such as describedin European patent application EP640619), DYNEPO™ (epoetin delta), humanerythropoietin analog (such as the human serum albumin fusion proteinsdescribed in international patent application WO9966054 and U.S. Pat.Nos. 6,548,653; and 5,888,772, which are incorporated by referenceherein), erythropoietin mutants (such as those described ininternational patent application WO9938890, and U.S. Pat. Nos.6,489,293; 5,888,772; 5,614,184; and 5,457,089 which are incorporated byreference herein), erythropoietin omega (which may be produced from anApa I restriction fragment of the human erythropoietin gene described inU.S. Pat. Nos. 5,688,679; 6,099,830; 6,316,254; and 6,682,910, which areincorporated by reference herein), altered glycosylated humanerythropoietin (such as those described in international patentapplication WO9911781 and EP1064951), and PEG conjugated erythropoietinanalogs (such as those described in WO9805363 and U.S. Pat. Nos.5,643,575; 6,583,272; 6,340,742; and 6,586,398, which are incorporatedby reference herein). Specific examples of cell lines modified forexpression of endogenous human erythropoietin are described ininternational patent applications WO9905268 and WO9412650 and U.S. Pat.No. 6,376,218 which are incorporated by reference herein.

The term “feline erythropoietin (fEPO)” or “fEPO polypeptide” refers toerythropoietin or EPO as described above, as well as a polypeptide thatretains at least one biological activity of naturally-occurring fEPO.fEPO polypeptides include the pharmaceutically acceptable salts andprodrugs, and prodrugs of the salts, polymorphs, hydrates, solvates,biologically-active fragments, biologically-active variants andstereoisomers of the naturally-occurring feline erythropoietin as wellas agonist, mimetic, and antagonist variants of the naturally-occurringhuman Erythropoietin and polypeptide fusions thereof. Examples of fEPOpolypeptides and mimetics include those described in U.S. Pat. Nos.6,310,078; 5,106,954; 6,703,480; 6,642,353; 5,986,047; and 5,712,370,which are incorporated by reference herein. Fusions comprisingadditional amino acids at the amino terminus, carboxyl terminus, orboth, are encompassed by the term “fEPO polypeptide.” Exemplary fusionsinclude, but are not limited to, e.g., methionyl erythropoietin in whicha methionine is linked to the N-terminus of fEPO, fusions for thepurpose of purification (including but not limited to, to poly-histadineor affinity epitopes), fusions with serum albumin binding peptides andfusions with serum proteins such as serum albumin. Thenaturally-occurring fEPO nucleic acid and amino acid sequences areknown. For the complete naturally-occurring fEPO amino acid sequence aswell as the mature naturally-occurring hEPO amino acid sequence, see SEQID NO:1 and SEQ ID NO:2, respectively, herein. For the completeconsensus fEPO amino acid sequence as well as the mature consensus fEPOamino acid sequence, see SEQ ID NO:3 and SEQ ID NO:4, respectively,herein. In some embodiments, fEPO polypeptides of the invention aresubstantially identical to SEQ ID NO:1, SEQ ID NO:2, SEQ ID NO:3, or SEQID NO:4. Nucleic acid molecules encoding fEPO mutants and mutant fEPOpolypeptides are known as well. Examples of fEPO mutants include thosedisclosed in U.S. Pat. Nos. 6,489,293; 6,153,407; 6,048,971; 5,614,184;and 5,457,089, which are incorporated by reference herein.

Erythropoietin or fEPO has a variety of biological activities includingbut not limited to binding to its receptor, causing dimerization of itsreceptor, stimulation of red blood cell production, and stimulating cellproliferation. Examples of some of the biological activities oferythropoietin and hEPO are described in U.S. Pat. Nos. 6,676,947;6,579,525; 6,531,121; 6,521,245; 6,489,293; 6,368,854; 6,316,254;6,268,336; 6,239,109; 6,165,283; 5,986,047; 5,830,851; and 5,773,569,which are incorporated by reference herein.

Biologically-active fragments/variants of fEPO include the gene productcontaining 192 amino acids, of which the first 26 are cleaved duringsecretion as well as the removal of one or more of the last four aminoacids during the formation of the mature form of erythropoietin (SEQ IDNO:1 and SEQ ID NO:2). The term “fEPO polypeptide” also includes theglycosylated forms, with N-linked glycosylation sites at 24, 38, and 83,and O-linked glycosylation site at 126 (Takeuchi et al. (1988) JBC 263:3657-3663; Saski et al. (1988) Biochemistry 27: 8618-8626). Variantscontaining single nucleotide changes (i.e. S104N and L105F, P122Q, E13Q,Q58→QQ, G113R) are also considered as biologically active variants ofhEPO (Jacobs et al., (1985) Nature 313: 806-810; Funakoshi et al.,(1993) Biochem. Biophys. Res. Comm 195: 717-722). The term “fEPOpolypeptide” also includes fEPO heterodimers, homodimers,heteromultimers, or homomultimers of fEPO or any other polypeptide,protein, carbohydrate, polymer, small molecule, ligand, or other activemolecule of any type, linked by chemical means or expressed as a fusionprotein (Sytkowski et al., (1998) Proc. Natl. Acad. Sci. USA95(3):1184-8, and Sytkowski et al. (1999) J. Biol. Chem.274(35):24773-8, and U.S. Pat. Nos. 6,187,564; 6,703,480; 5,767,078which are incorporated by reference herein), as well as polypeptideanalogues containing specific deletions, yet maintain biologicalactivity (Boissel et al., (1993) JBC 268: 15983-15993; Wen et al.,(1994) JBC 269: 22839-22846; Bittorf et al., (1993) FEBS 336: 133-136;and U.S. Pat. No. 6,153,407 which is incorporated by reference herein).

All references to amino acid positions in fEPO described herein arebased on the position in SEQ ID NO: 2, unless otherwise specified (i.e.,when it is stated that the comparison is based on SEQ ID NO: 3). Thoseof skill in the art will appreciate that amino acid positionscorresponding to positions in SEQ ID NO: 2 can be readily identified infEPO fusions, variants, fragments, etc. For example, sequence alignmentprograms such as BLAST can be used to align and identify a particularposition in a protein that corresponds with a position in SEQ ID NO:2.Substitutions, deletions or additions of amino acids described herein inreference to SEQ ID NO: 2 are intended to also refer to substitutions,deletions or additions in corresponding positions in fEPO fusions,variants, fragments, etc. described herein or known in the art and areexpressly encompassed by the present invention.

The term “fEPO polypeptide” encompasses fEPO polypeptides comprising oneor more amino acid substitutions, additions or deletions. Exemplarysubstitutions in a wide variety of amino acid positions innaturally-occurring fEPO have been described, including but not limitedto substitutions that increase agonist activity, increase solubility ofthe polypeptide, convert the polypeptide into an antagonist, etc. andare encompassed by the term “fEPO polypeptide.”

Feline EPO antagonists include, but are not limited to, those with asubstitutions at V11, R14, Y15, D96, K97, S100, R103, S104, T107, L108,and R110 (including but not limited to, V11S, R14Q, Y15I, S100E, R103A,S104I, and L108K, see Elliot et al. 1993) found in the low affinityreceptor binding site (site 2). In some embodiments, fEPO antagonistscomprise at least one substitution in the regions 10-15 or 100-108 thatcause fEPO to act as an antagonist. See, e.g., Elliot et al. 1993 andCheetham et al. 1998. In some embodiments, the fEPO antagonist comprisesa non-naturally encoded amino acid linked to a water soluble polymerthat is present in the Site 2 binding region of the hEPO molecule. Insome embodiments, the fEPO polypeptide is even further modified bycontaining the following substitutions: V11S, R14Q, Y15I, S100E, R103A,S104I, and L108K.

In some embodiments, the fEPO polypeptides further comprise an addition,substitution or deletion that modulates biological activity of fEPO. Forexample, the additions, substitutions or deletions may modulate affinityfor the fEPO receptor, modulate (including but not limited to, increasesor decreases) receptor dimerization, stabilize receptor dimers, modulatecirculating half-life, modulate therapeutic half-life, modulatestability of the polypeptide, modulate dose, modulate release orbio-availability, facilitate purification, or improve or alter aparticular route of administration. Similarly, fEPO polypeptides maycomprise protease cleavage sequences, reactive groups, antibody-bindingdomains (including but not limited to, FLAG or poly-His) or otheraffinity based sequences (including but not limited to, FLAG, poly-His,GST, etc.) or linked molecules (including but not limited to, biotin)that improve detection (including but not limited to, GFP), purificationor other traits of the polypeptide.

The term “fEPO polypeptide” also encompasses fEPO homodimers,heterodimers, homomultimers, and heteromultimers linked directly vianon-naturally encoded amino acid side chains, either to the same ordifferent non-naturally encoded amino acid side chains, tonaturally-encoded amino acid side chains, or indirectly via a linker.Exemplary linkers including but are not limited to, water solublepolymers such as poly(ethylene glycol) or polydextran or a polypeptide.

A “non-naturally encoded amino acid” refers to an amino acid that is notone of the 20 common amino acids or pyrolysine or selenocysteine. Theterm “non-naturally encoded amino acid” includes, but is not limited to,amino acids that occur naturally by modification of a naturally encodedamino acid (including but not limited to, the 20 common amino acids orpyrolysine and selenocysteine) but are not themselves incorporated intoa growing polypeptide chain by the translation complex. Examples ofnaturally-occurring amino acids that are not naturally-encoded include,but are not limited to, N-acetylglucosaminyl-L-serine,N-acetylglucosaminyl-L-threonine, and O-phosphotyrosine.

An “amino terminus modification group” refers to any molecule that canbe attached to the amino terminus of a polypeptide. Similarly, a“carboxy terminus modification group” refers to any molecule that can beattached to the carboxy terminus of a polypeptide. Terminus modificationgroups include but are not limited to various water soluble polymers,peptides or proteins such as serum albumin, or other moieties thatincrease serum half-life of peptides.

The terms “functional group”, “active moiety”, “activating group”,“leaving group”, “reactive site”, “chemically reactive group” and“chemically reactive moiety” are used in the art and herein to refer todistinct, definable portions or units of a molecule. The terms aresomewhat synonymous in the chemical arts and are used herein to indicatethe portions of molecules that perform some function or activity and arereactive with other molecules.

The term “linkage” or “linker” is used herein to refer to groups orbonds that normally are formed as the result of a chemical reaction andtypically are covalent linkages. Hydrolytically stable linkages meansthat the linkages are substantially stable in water and do not reactwith water at useful pH values, including but not limited to, underphysiological conditions for an extended period of time, perhaps evenindefinitely. Hydrolytically unstable or degradable linkages means thatthe linkages are degradable in water or in aqueous solutions, includingfor example, blood. Enzymatically unstable or degradable linkages meansthat the linkage can be degraded by one or more enzymes. As understoodin the art, PEG and related polymers may include degradable linkages inthe polymer backbone or in the linker group between the polymer backboneand one or more of the terminal functional groups of the polymermolecule. For example, ester linkages formed by the reaction of PEGcarboxylic acids or activated PEG carboxylic acids with alcohol groupson a biologically active agent generally hydrolyze under physiologicalconditions to release the agent. Other hydrolytically degradablelinkages include but are not limited to carbonate linkages; iminelinkages resulted from reaction of an amine and an aldehyde; phosphateester linkages formed by reacting an alcohol with a phosphate group;hydrazone linkages which are reaction product of a hydrazide and analdehyde; acetal linkages that are the reaction product of an aldehydeand an alcohol; orthoester linkages that are the reaction product of aformate and an alcohol; peptide linkages formed by an amine group,including but not limited to, at an end of a polymer such as PEG, and acarboxyl group of a peptide; and oligonucleotide linkages formed by aphosphoramidite group, including but not limited to, at the end of apolymer, and a 5′ hydroxyl group of an oligonucleotide.

The term “biologically active molecule”, “biologically active moiety” or“biologically active agent” when used herein means any substance whichcan affect any physical or biochemical properties of a biologicalorganism, including but not limited to viruses, bacteria, fungi, plants,animals, and humans. In particular, as used herein, biologically activemolecules include but are not limited to any substance intended fordiagnosis, cure, mitigation, treatment, or prevention of disease inhumans or other animals, or to otherwise enhance physical or mentalwell-being of humans or animals. Examples of biologically activemolecules include, but are not limited to, peptides, proteins, enzymes,small molecule drugs, dyes, lipids, nucleosides, oligonucleotides,cells, viruses, liposomes, microparticles and micelles. Classes ofbiologically active agents that are suitable for use with the inventioninclude, but are not limited to, antibiotics, fungicides, anti-viralagents, anti-inflammatory agents, anti-tumor agents, cardiovascularagents, anti-anxiety agents, hormones, growth factors, steroidal agents,and the like.

A “bifunctional polymer” refers to a polymer comprising two discretefunctional groups that are capable of reacting specifically with othermoieties (including but not limited to, amino acid side groups) to formcovalent or non-covalent linkages. A bifunctional linker having onefunctional group reactive with a group on a particular biologicallyactive component, and another group reactive with a group on a secondbiological component, may be used to form a conjugate that includes thefirst biologically active component, the bifunctional linker and thesecond biologically active component. Many procedures and linkermolecules for attachment of various compounds to peptides are known.See, e.g., European Patent Application No. 188,256; U.S. Pat. Nos.4,671,958, 4,659,839, 4,414,148, 4,699,784; 4,680,338; 4,569,789; and4,589,071 which are incorporated by reference herein. A“multi-functional polymer” refers to a polymer comprising two or morediscrete functional groups that are capable of reacting specificallywith other moieties (including but not limited to, amino acid sidegroups) to form covalent or non-covalent linkages.

Where substituent groups are specified by their conventional chemicalformulas, written from left to right, they equally encompass thechemically identical substituents that would result from writing thestructure from right to left, for example, —CH₂O— is equivalent to—OCH₂—.

The term “substituents” includes but is not limited to “non-interferingsubstituents”. “Non-interfering substituents” are those groups thatyield stable compounds. Suitable non-interfering substituents orradicals include, but are not limited to, halo, C₁-C₁₀ alkyl, C₂-C₁₀alkenyl, C₂-C₁₀ alkynyl, C₁-C₁₀ alkoxy, C₁-C₁₂ aralkyl, C₁-C₁₂ alkaryl,C₃-C₁₂ cycloalkyl, C₃-C₁₂ cycloalkenyl, phenyl, substituted phenyl,toluoyl, xylenyl, biphenyl, C₂-C₁₂ alkoxyalkyl, C₂-C₁₂ alkoxyaryl,C₇-C₁₂ aryloxyalkyl, C₇-C₁₂ oxyaryl, C₁-C₆ alkylsulfinyl, C₁-C₁₀alkylsulfonyl, —(CH₂)_(m) —O—(C₁-C₁₀ alkyl) wherein m is from 1 to 8,aryl, substituted aryl, substituted alkoxy, fluoroalkyl, heterocyclicradical, substituted heterocyclic radical, nitroalkyl, ——NO₂, —CN,—NRC(O)—(C₁-C₁₀ alkyl), —C(O)—(C₁-C₁₀ alkyl), C₂-C₁₀ alkyl thioalkyl,—C(O)O—(C₁-C₁₀ alkyl), —OH, —SO₂, ═S, —COOH, —NR₂, carbonyl,—C(O)—(C₁-C₁₀ alkyl)-CF3, —C(O)—CF3, —C(O)NR2, —(C₁-C₁₀ aryl)-S—(C₆-C₁₀aryl), —C(O)—(C₁-C₁₀ aryl), —(CH₂)_(m) —O—(—(CH₂)_(m)—O—(C₁-C₁₀ alkyl)wherein each m is from 1 to 8, —C(O)NR₂, —C(S)NR₂, —SO₂NR₂, —NRC(O)NR₂,—NRC(S)NR₂, salts thereof, and the like. Each R as used herein is H,alkyl or substituted alkyl, aryl or substituted aryl, aralkyl, oralkaryl.

The term “halogen” includes fluorine, chlorine, iodine, and bromine.

The term “alkyl,” by itself or as part of another substituent, means,unless otherwise stated, a straight or branched chain, or cyclichydrocarbon radical, or combination thereof, which may be fullysaturated, mono- or polyunsaturated and can include di- and multivalentradicals, having the number of carbon atoms designated (i.e. C₁-C₁₀means one to ten carbons). Examples of saturated hydrocarbon radicalsinclude, but are not limited to, groups such as methyl, ethyl, n-propyl,isopropyl, n-butyl, t-butyl, isobutyl, sec-butyl, cyclohexyl,(cyclohexyl)methyl, cyclopropylmethyl, homologs and isomers of, forexample, n-pentyl, n-hexyl, n-heptyl, n-octyl, and the like. Anunsaturated alkyl group is one having one or more double bonds or triplebonds. Examples of unsaturated alkyl groups include, but are not limitedto, vinyl, 2-propenyl, crotyl, 2-isopentenyl, 2-(butadienyl),2,4-pentadienyl, 3-(1,4-pentadienyl), ethynyl, 1- and 3-propynyl,3-butynyl, and the higher homologs and isomers. The term “alkyl,” unlessotherwise noted, is also meant to include those derivatives of alkyldefined in more detail below, such as “heteroalkyl.” Alkyl groups whichare limited to hydrocarbon groups are termed “homoalkyl”.

The term “alkylene” by itself or as part of another substituent means adivalent radical derived from an alkane, as exemplified, but notlimited, by the structures —CH₂CH₂— and —CH₂CH₂CH₂CH₂—, and furtherincludes those groups described below as “heteroalkylene.” Typically, analkyl (or alkylene) group will have from 1 to 24 carbon atoms, withthose groups having 10 or fewer carbon atoms being preferred in thepresent invention. A “lower alkyl” or “lower alkylene” is a shorterchain alkyl or alkylene group, generally having eight or fewer carbonatoms.

The terms “alkoxy,” “alkylamino” and “alkylthio” (or thioalkoxy) areused in their conventional sense, and refer to those alkyl groupsattached to the remainder of the molecule via an oxygen atom, an aminogroup, or a sulfur atom, respectively.

The term “heteroalkyl,” by itself or in combination with another term,means, unless otherwise stated, a stable straight or branched chain, orcyclic hydrocarbon radical, or combinations thereof, consisting of thestated number of carbon atoms and at least one heteroatom selected fromthe group consisting of O, N, Si and S, and wherein the nitrogen andsulfur atoms may optionally be oxidized and the nitrogen heteroatom mayoptionally be quaternized. The heteroatom(s) O, N and S and Si may beplaced at any interior position of the heteroalkyl group or at theposition at which the alkyl group is attached to the remainder of themolecule. Examples include, but are not limited to, —CH₂—CH₂—O—CH₃,—CH₂—CH₂—NH—CH₃, —CH₂—CH₂—N(CH₃)—CH₃, —CH₂—S—CH₂—CH₃, —CH₂—CH₂,—S(O)—CH₃, —CH₂—CH₂—S(O)₂—CH₃, —CH═CH—O—CH₃, —Si(CH₃)₃, —CH₂—CH═N—OCH₃,and —CH═CH—N(CH₃)—CH₃. Up to two heteroatoms may be consecutive, suchas, for example, —CH₂—NH—OCH₃ and —CH₂—O—Si(CH₃)₃. Similarly, the term“heteroalkylene” by itself or as part of another substituent means adivalent radical derived from heteroalkyl, as exemplified, but notlimited by, —CH₂—CH₂—S—CH₂—CH₂— and —CH₂—S—CH₂—CH₂—NH—CH₂—. Forheteroalkylene groups, the same or different heteroatoms can also occupyeither or both of the chain termini (including but not limited to,alkyleneoxy, alkylenedioxy, alkyleneamino, alkylenediamino,aminooxyalkylene, and the like). Still further, for alkylene andheteroalkylene linking groups, no orientation of the linking group isimplied by the direction in which the formula of the linking group iswritten. For example, the formula —C(O)₂R′— represents both —C(O)₂R′—and —R′C(O)₂—.

The terms “cycloalkyl” and “heterocycloalkyl”, by themselves or incombination with other terms, represent, unless otherwise stated, cyclicversions of “alkyl” and “heteroalkyl”, respectively. Thus, a cycloalkylor heterocycloalkyl include saturated and unsaturated ring linkages.Additionally, for heterocycloalkyl, a heteroatom can occupy the positionat which the heterocycle is attached to the remainder of the molecule.Examples of cycloalkyl include, but are not limited to, cyclopentyl,cyclohexyl, 1-cyclohexenyl, 3-cyclohexenyl, cycloheptyl, and the like.Examples of heterocycloalkyl include, but are not limited to,1-(1,2,5,6-tetrahydropyridyl), 1-piperidinyl, 2-piperidinyl,3-piperidinyl, 4-morpholinyl, 3-morpholinyl, tetrahydrofuran-2-yl,tetrahydrofuran-3-yl, tetrahydrothien-2-yl, tetrahydrothien-3-yl,1-piperazinyl, 2-piperazinyl, and the like.

As used herein, the term “water soluble polymer” refers to any polymerthat is soluble in aqueous solvents. Linkage of water soluble polymersto fEPO can result in changes including, but not limited to, increasedor modulated serum half-life, or increased or modulated therapeutichalf-life relative to the unmodified form, modulated immunogenicity,modulated physical association characteristics such as aggregation andmultimer formation, altered receptor binding and altered receptordimerization or multimerization. The water soluble polymer may or maynot have its own biological activity. Suitable polymers include, but arenot limited to, polyethylene glycol, polyethylene glycolpropionaldehyde, mono C1-C10 alkoxy or aryloxy derivatives thereof(described in U.S. Pat. No. 5,252,714 which is incorporated by referenceherein), monomethoxy-polyethylene glycol, polyvinyl pyrrolidone,polyvinyl alcohol, polyamino acids, divinylether maleic anhydride,N-(2-Hydroxypropyl)-methacrylamide, dextran, dextran derivativesincluding dextran sulfate, polypropylene glycol, polypropyleneoxide/ethylene oxide copolymer, polyoxyethylated polyol, heparin,heparin fragments, polysaccharides, oligosaccharides, glycans, celluloseand cellulose derivatives, including but not limited to methylcelluloseand carboxymethyl cellulose, starch and starch derivatives,polypeptides, polyalkylene glycol and derivatives thereof, copolymers ofpolyalkylene glycols and derivatives thereof, polyvinyl ethyl ethers,and alpha-beta-poly[(2-hydroxyethyl)-DL-aspartamide, and the like, ormixtures thereof. Examples of such water soluble polymers include butare not limited to polyethylene glycol and serum albumin.

As used herein, the term “polyalkylene glycol” refers to polyethyleneglycol, polypropylene glycol, polybutylene glycol, and derivativesthereof. The term “polyalkylene glycol” encompasses both linear andbranched polymers and average molecular weights of between 1 kDa and 100kDa. Other exemplary embodiments are listed, for example, in commercialsupplier catalogs, such as Shearwater Corporation's catalog“Polyethylene Glycol and Derivatives for Biomedical Applications”(2001).

The term “aryl” means, unless otherwise stated, a polyunsaturated,aromatic, hydrocarbon substituent which can be a single ring or multiplerings (preferably from 1 to 3 rings) which are fused together or linkedcovalently. The term “heteroaryl” refers to aryl groups (or rings) thatcontain from one to four heteroatoms selected from N, O, and S, whereinthe nitrogen and sulfur atoms are optionally oxidized, and the nitrogenatom(s) are optionally quaternized. A heteroaryl group can be attachedto the remainder of the molecule through a heteroatom. Non-limitingexamples of aryl and heteroaryl groups include phenyl, 1-naphthyl,2-naphthyl, 4-biphenyl, 1-pyrrolyl, 2-pyrrolyl, 3-pyrrolyl, 3-pyrazolyl,2-imidazolyl, 4-imidazolyl, pyrazinyl, 2-oxazolyl, 4-oxazolyl,2-phenyl-4-oxazolyl, 5-oxazolyl, 3-isoxazolyl, 4-isoxazolyl,5-isoxazolyl, 2-thiazolyl, 4-thiazolyl, 5-thiazolyl, 2-furyl, 3-furyl,2-thienyl, 3-thienyl, 2-pyridyl, 3-pyridyl, 4-pyridyl, 2-pyrimidyl,4-pyrimidyl, 5-benzothiazolyl, purinyl, 2-benzimidazolyl, 5-indolyl,1-isoquinolyl, 5-isoquinolyl, 2-quinoxalinyl, 5-quinoxalinyl,3-quinolyl, and 6-quinolyl. Substituents for each of the above notedaryl and heteroaryl ring systems are selected from the group ofacceptable substituents described below.

For brevity, the term “aryl” when used in combination with other terms(including but not limited to, aryloxy, arylthioxy, arylalkyl) includesboth aryl and heteroaryl rings as defined above. Thus, the term“arylalkyl” is meant to include those radicals in which an aryl group isattached to an alkyl group (including but not limited to, benzyl,phenethyl, pyridylmethyl and the like) including those alkyl groups inwhich a carbon atom (including but not limited to, a methylene group)has been replaced by, for example, an oxygen atom (including but notlimited to, phenoxymethyl, 2-pyridyloxymethyl, 3-(1-naphthyloxy)propyl,and the like).

Each of the above teams (including but not limited to, “alkyl,”“heteroalkyl,” “aryl” and “heteroaryl”) are meant to include bothsubstituted and unsubstituted forms of the indicated radical. Exemplarysubstituents for each type of radical are provided below.

Substituents for the alkyl and heteroalkyl radicals (including thosegroups often referred to as alkylene, alkenyl, heteroalkylene,heteroalkenyl, alkynyl, cycloalkyl, heterocycloalkyl, cycloalkenyl, andheterocycloalkenyl) can be one or more of a variety of groups selectedfrom, but not limited to: —OR′, ═O, ═NR′, ═N—OR′, —NR′R″, —SR′,-halogen, —SiR′R″R′″, —OC(O)R′, —C(O)R′, —CO₂R′, —CONR′R″, —OC(O)NR′R″,—NR″C(O)R′, —-NR′—C(O)NR″R′″, —NR″C(O)₂R′, —NR—C(NR′R″R′″)═NR′″,—NR—C(NR′R″)═NR′″, —S(O)R′, —S(O)₂R′, —S(O)₂NR′R″, —NRSO₂R′, —CN and—NO₂ in a number ranging from zero to (2m′+1), where m′ is the totalnumber of carbon atoms in such a radical. R′, R″, R′″ and R″″ eachindependently refer to hydrogen, substituted or unsubstitutedheteroalkyl, substituted or unsubstituted aryl, including but notlimited to, aryl substituted with 1-3 halogens, substituted orunsubstituted alkyl, alkoxy or thioalkoxy groups, or arylalkyl groups.When a compound of the invention includes more than one R group, forexample, each of the R groups is independently selected as are each R′,R″, R′″ and R″″ groups when more than one of these groups is present.When R′ and R″ are attached to the same nitrogen atom, they can becombined with the nitrogen atom to form a 5-, 6-, or 7-membered ring.For example, —NR′R″ is meant to include, but not be limited to,1-pyrrolidinyl and 4-morpholinyl. From the above discussion ofsubstituents, one of skill in the art will understand that the term“alkyl” is meant to include groups including carbon atoms bound togroups other than hydrogen groups, such as haloalkyl (including but notlimited to, —CF₃ and —CH₂CF₃) and acyl (including but not limited to,—C(O)CH₃, —C(O)CF₃, —C(O)CH₂OCH₃, and the like).

Similar to the substituents described for the alkyl radical,substituents for the aryl and heteroaryl groups are varied and areselected from, but are not limited to: halogen, —OR′, ═O, ═NR′, ′N—OR′,—NR′R″, —SR′, -halogen, —SiR′R″R′″, —OC(O)R′, —C(O)R′, —CO₂R′, —CONR′R″,—OC(O)NR′R″, —NR″C(O)R′, —NR′—C(O)NR″R′″, —NR″C(O)₂R′,—NR—C(NR′R″R″″)═NR″″, —NR—C(NR′R″)═NR′″, —S(O)R′, —S(O)₂R′, —S(O)₂NR′R″,—NRSO₂R′, —CN and —NO₂, —R′, —N₃, —CH(Ph)₂, fluoro(C₁-C₄)alkoxy, andfluoro(C₁-C₄)alkyl, in a number ranging from zero to the total number ofopen valences on the aromatic ring system; and where R′, R″, R′″ and R″″are independently selected from hydrogen, alkyl, heteroalkyl, aryl andheteroaryl. When a compound of the invention includes more than one Rgroup, for example, each of the R groups is independently selected asare each R′, R″, R′″ and R″″ groups when more than one of these groupsis present.

As used herein, the term “modulated serum half-life” means the positiveor negative change in circulating half-life of a modified biologicallyactive molecule relative to its non-modified form. Serum half-life ismeasured by taking blood samples at various time points afteradministration of the biologically active molecule, and determining theconcentration of that molecule in each sample. Correlation of the serumconcentration with time allows calculation of the serum half-life.Increased serum half-life desirably has at least about two-fold, but asmaller increase may be useful, for example where it enables asatisfactory dosing regimen or avoids a toxic effect. In someembodiments, the increase is at least about three-fold, at least aboutfive-fold, or at least about ten-fold.

The term “modulated therapeutic half-life” as used herein means thepositive or negative change in the half-life of the therapeuticallyeffective amount of a modified biologically active molecule, relative toits non-modified form. Therapeutic half-life is measured by measuringpharmacokinetic and/or pharmacodynamic properties of the molecule atvarious time points after administration. Increased therapeutichalf-life desirably enables a particular beneficial dosing regimen, aparticular beneficial total dose, or avoids an undesired effect. In someembodiments, the increased therapeutic half-life results from increasedpotency, increased or decreased binding of the modified molecule to itstarget, or an increase or decrease in another parameter or mechanism ofaction of the non-modified molecule.

The term “isolated,” when applied to a nucleic acid or protein, denotesthat the nucleic acid or protein is substantially free of other cellularcomponents with which it is associated in the natural state. It can bein a homogeneous state. Isolated substances can be in either a dry orsemi-dry state, or in solution, including but not limited to an aqueoussolution. Purity and homogeneity are typically determined usinganalytical chemistry techniques such as polyacrylamide gelelectrophoresis or high performance liquid chromatography. A proteinwhich is the predominant species present in a preparation issubstantially purified. In particular, an isolated gene is separatedfrom open reading frames which flank the gene and encode a protein otherthan the gene of interest. The term “purified” denotes that a nucleicacid or protein gives rise to substantially one band in anelectrophoretic gel. Particularly, it means that the nucleic acid orprotein is at least 85% pure, at least 90% pure, at least 95% pure, orat least 99% pure or greater.

The term “nucleic acid” refers to deoxyribonucleotides orribonucleotides and polymers thereof in either single- ordouble-stranded form. Unless specifically limited, the term encompassesnucleic acids containing known analogues of natural nucleotides whichhave similar binding properties as the reference nucleic acid and aremetabolized in a manner similar to naturally occurring nucleotides.Unless otherwise indicated, a particular nucleic acid sequence alsoimplicitly encompasses conservatively modified variants thereof(including but not limited to, degenerate codon substitutions) andcomplementary sequences as well as the sequence explicitly indicated.Specifically, degenerate codon substitutions may be achieved bygenerating sequences in which the third position of one or more selected(or all) codons is substituted with mixed-base and/or deoxyinosineresidues (Batzer et al., Nucleic Acid Res. 19:5081 (1991); Ohtsuka etal., J. Biol. Chem. 260:2605-2608 (1985); and Cassol et al. (1992);Rossolini et al., Mol. Cell. Probes 8:91-98 (1994)).

The terms “polypeptide,” “peptide” and “protein” are usedinterchangeably herein to refer to a polymer of amino acid residues. Theterms apply to naturally occurring amino acid polymers as well as aminoacid polymers in which one or more amino acid residues is anon-naturally encoded amino acid. As used herein, the terms encompassamino acid chains of any length, including full length proteins (i.e.,antigens), wherein the amino acid residues are linked by covalentpeptide bonds.

Antibodies are proteins, which exhibit binding specificity to a specificantigen. Native antibodies are usually heterotetrameric glycoproteins ofabout 150,000 daltons, composed of two identical light (L) chains andtwo identical heavy (H) chains. Each light chain is linked to a heavychain by one covalent disulfide bond, while the number of disulfidelinkages varies between the heavy chains of different immunoglobulinisotypes. Each heavy and light chain also has regularly spacedintrachain disulfide bridges. Each heavy chain has at one end a variabledomain (V_(H)) followed by a number of constant domains. Each lightchain has a variable domain at one end (V_(L)) and a constant domain atits other end; the constant domain of the light chain is aligned withthe first constant domain of the heavy chain, and the light chainvariable domain is aligned with the variable domain of the heavy chain.Particular amino acid residues are believed to form an interface betweenthe light and heavy chain variable domains.

The term “variable” refers to the fact that certain portions of thevariable domains differ extensively in sequence among antibodies and areresponsible for the binding specificity of each particular antibody forits particular antigen. However, the variability is not evenlydistributed through the variable domains of antibodies. It isconcentrated in three segments called Complementarity DeterminingRegions (CDRs) both in the light chain and the heavy chain variabledomains. The more highly conserved portions of the variable domains arecalled the framework regions (FR). The variable domains of native heavyand light chains each comprise four FR regions, largely adopting aβ-sheet configuration, connected by three or four CDRs, which form loopsconnecting, and in some cases forming part of, the β-sheet structure.The CDRs in each chain are held together in close proximity by the FRregions and, with the CDRs from the other chain, contribute to theformation of the antigen binding site of antibodies (see Kabat et al.,Sequences of Proteins of Immunological Interest, 5th Ed. Public HealthService, National Institutes of Health, Bethesda, Md. (1991)).

The constant domains are not involved directly in binding an antibody toan antigen, but exhibit various effector functions. Depending on theamino acid sequence of the constant region of their heavy chains,antibodies or immunoglobulins can be assigned to different classes.There are five major classes of immunoglobulins: IgA, IgD, IgE, IgG andIgM, and several of these may be further divided into subclasses(isotypes), e.g. IgG1, IgG2, IgG3, and IgG4; IgA1 and IgA2. The heavychain constant regions that correspond to the different classes ofimmunoglobulins are called α, δ, ε, γ and μ, respectively. Of thevarious human immunoglobulin classes, only human IgG1, IgG2, IgG3 andIgM are known to activate complement.

In vivo, affinity maturation of antibodies is driven by antigenselection of higher affinity antibody variants which are made primarilyby somatic hypermutagenesis. A “repertoire shift” also often occurs inwhich the predominant germline genes of the secondary or tertiaryresponse are seen to differ from those of the primary or secondaryresponse.

The affinity maturation process of the immune system may be replicatedby introducing mutations into antibody genes in vitro and using affinityselection to isolate mutants with improved affinity. Such mutantantibodies can be displayed on the surface of filamentous bacteriophageor microorganisms such as yeast, and antibodies can be selected by theiraffinity for antigen or by their kinetics of dissociation (off-rate)from antigen. Hawkins et al. J. Mol. Biol. 226:889-896 (1992). CDRwalking mutagenesis has been employed to affinity mature humanantibodies which bind the human envelope glycoprotein gp120 of humanimmunodeficiency virus type 1 (HIV-1) (Barbas III et al. PNAS (USA) 91:3809-3813 (1994); and Yang et al. J. Mol. Biol. 254:392-403 (1995)); andan anti-c-erbB-2 single chain Fv fragment (Schier et al. J. Mol. Biol.263:551567 (1996)). Antibody chain shuffling and CDR mutagenesis wereused to affinity mature a high-affinity human antibody directed againstthe third hypervariable loop of HIV (Thompson et al. J. Mol. Biol.256:77-88 (1996)). Balint and Larrick Gene 137:109-118 (1993) describe acomputer-assisted oligodeoxyribonucleotide-directed scanning mutagenesiswhereby all CDRs of a variable region gene are simultaneously andthoroughly searched for improved variants. An αvβ3-specific humanizedantibody was affinity matured using an initial limited mutagenesisstrategy in which every position of all six CDRs was mutated followed bythe expression and screening of a combinatorial library including thehighest affinity mutants (Wu et al. PNAS (USA) 95: 6037-6-42 (1998)).Phage displayed antibodies are reviewed in Chiswell and McCaffertyTIBTECH 10:80-84 (1992); and Rader and Barbas III Current Opinion inBiotech. 8:503-508 (1997). In each case where mutant antibodies withimproved affinity compared to a parent antibody are reported in theabove references, the mutant antibody has amino acid substitutions in aCDR.

By “affinity maturation” herein is meant the process of enhancing theaffinity of an antibody for its antigen. Methods for affinity maturationinclude but are not limited to computational screening methods andexperimental methods.

By “antibody” herein is meant a protein consisting of one or morepolypeptides substantially encoded by all or part of the antibody genes.The immunoglobulin genes include, but are not limited to, the kappa,lambda, alpha, gamma (IgG1, IgG2, IgG3, and IgG4), delta, epsilon and muconstant region genes, as well as the myriad immunoglobulin variableregion genes. Antibody herein is meant to include full-length antibodiesand antibody fragments, and include antibodies that exist naturally inany organism or are engineered (e.g. are variants).

By “antibody fragment” is meant any form of an antibody other than thefull-length form. Antibody fragments herein include antibodies that aresmaller components that exist within full-length antibodies, andantibodies that have been engineered. Antibody fragments include but arenot limited to Fv, Fc, Fab, and (Fab′)₂, single chain Fv (scFv),diabodies, triabodies, tetrabodies, bifunctional hybrid antibodies,CDR1, CDR2, CDR3, combinations of CDR's, variable regions, frameworkregions, constant regions, and the like (Maynard & Georgiou, 2000, Annu.Rev. Biomed. Eng. 2:339-76; Hudson, 1998, Curr. Opin. Biotechnol.9:395-402).

The term “amino acid” refers to naturally occurring and non-naturallyoccurring amino acids, as well as amino acid analogs and amino acidmimetics that function in a manner similar to the naturally occurringamino acids. Naturally encoded amino acids are the 20 common amino acids(alanine, arginine, asparagine, aspartic acid, cysteine, glutamine,glutamic acid, glycine, histidine, isoleucine, leucine, lysine,methionine, phenylalanine, proline, serine, threonine, tryptophan,tyrosine, and valine) and pyrolysine and selenocysteine. Amino acidanalogs refers to compounds that have the same basic chemical structureas a naturally occurring amino acid, i.e., an a carbon that is bound toa hydrogen, a carboxyl group, an amino group, and an R group, such as,homoserine, norleucine, methionine sulfoxide, methionine methylsulfonium. Such analogs have modified R groups (such as, norleucine) ormodified peptide backbones, but retain the same basic chemical structureas a naturally occurring amino acid.

Amino acids may be referred to herein by either their commonly knownthree letter symbols or by the one-letter symbols recommended by theIUPAC-IUB Biochemical Nomenclature Commission. Nucleotides, likewise,may be referred to by their commonly accepted single-letter codes.

“Conservatively modified variants” applies to both amino acid andnucleic acid sequences. With respect to particular nucleic acidsequences, “conservatively modified variants” refers to those nucleicacids which encode identical or essentially identical amino acidsequences, or where the nucleic acid does not encode an amino acidsequence, to essentially identical sequences. Because of the degeneracyof the genetic code, a large number of functionally identical nucleicacids encode any given protein. For instance, the codons GCA, GCC, GCGand GCU all encode the amino acid alanine. Thus, at every position wherean alanine is specified by a codon, the codon can be altered to any ofthe corresponding codons described without altering the encodedpolypeptide. Such nucleic acid variations are “silent variations,” whichare one species of conservatively modified variations. Every nucleicacid sequence herein which encodes a polypeptide also describes everypossible silent variation of the nucleic acid. One of skill willrecognize that each codon in a nucleic acid (except AUG, which isordinarily the only codon for methionine, and TGG, which is ordinarilythe only codon for tryptophan) can be modified to yield a functionallyidentical molecule. Accordingly, each silent variation of a nucleic acidwhich encodes a polypeptide is implicit in each described sequence.

As to amino acid sequences, one of skill will recognize that individualsubstitutions, deletions or additions to a nucleic acid, peptide,polypeptide, or protein sequence which alters, adds or deletes a singleamino acid or a small percentage of amino acids in the encoded sequenceis a “conservatively modified variant” where the alteration results inthe substitution of an amino acid with a chemically similar amino acid.Conservative substitution tables providing functionally similar aminoacids are well known in the art. Such conservatively modified variantsare in addition to and do not exclude polymorphic variants, interspecieshomologs, and alleles of the invention.

The following eight groups each contain amino acids that areconservative substitutions for one another:

-   1) Alanine (A), Glycine (G);-   2) Aspartic acid (D), Glutamic acid (E);-   3) Asparagine (N), Glutamine (Q);-   4) Arginine (R), Lysine (K);-   5) Isoleucine (I), Leucine (L), Methionine (M), Valine (V);-   6) Phenylalanine (F), Tyrosine (Y), Tryptophan (W);-   7) Serine (S), Threonine (T); and-   8) Cysteine (C), Methionine (M)    (see, e.g., Creighton, Proteins: Structures and Molecular Properties    (W H Freeman & Co.; 2nd edition (December 1993)

The terms “identical” or percent “identity,” in the context of two ormore nucleic acids or polypeptide sequences, refer to two or moresequences or subsequences that are the same. Sequences are“substantially identical” if they have a percentage of amino acidresidues or nucleotides that are the same (i.e., about 60% identity,optionally about 65%, about 70%, about 75%, about 80%, about 85%, about90%, or about 95% identity over a specified region), when compared andaligned for maximum correspondence over a comparison window, ordesignated region as measured using one of the following sequencecomparison algorithms or by manual alignment and visual inspection. Thisdefinition also refers to the complement of a test sequence. Theidentity can exist over a region that is at least about 50 amino acidsor nucleotides in length, or over a region that is 75-100 amino acids ornucleotides in length, or, where not specified, across the entiresequence or a polynucleotide or polypeptide.

For sequence comparison, typically one sequence acts as a referencesequence, to which test sequences are compared. When using a sequencecomparison algorithm, test and reference sequences are entered into acomputer, subsequence coordinates are designated, if necessary, andsequence algorithm program parameters are designated. Default programparameters can be used, or alternative parameters can be designated. Thesequence comparison algorithm then calculates the percent sequenceidentities for the test sequences relative to the reference sequence,based on the program parameters.

A “comparison window”, as used herein, includes reference to a segmentof any one of the number of contiguous positions selected from the groupconsisting of from 20 to 600, usually about 50 to about 200, moreusually about 100 to about 150 in which a sequence may be compared to areference sequence of the same number of contiguous positions after thetwo sequences are optimally aligned. Methods of alignment of sequencesfor comparison are well-known in the art. Optimal alignment of sequencesfor comparison can be conducted, including but not limited to, by thelocal homology algorithm of Smith and Waterman (1970) Adv. Appl. Math.2:482c, by the homology alignment algorithm of Needleman and Wunsch(1970) J. Mol. Biol. 48:443, by the search for similarity method ofPearson and Lipman (1988) Proc. Nat'l. Acad. Sci. USA 85:2444, bycomputerized implementations of these algorithms (GAP, BESTFIT, FASTA,and TFASTA in the Wisconsin Genetics Software Package, Genetics ComputerGroup, 575 Science Dr., Madison, Wis.), or by manual alignment andvisual inspection (see, e.g., Ausubel et al., Current Protocols inMolecular Biology (1995 supplement)).

One example of an algorithm that is suitable for determining percentsequence identity and sequence similarity are the BLAST and BLAST 2.0algorithms, which are described in Altschul et al. (1977) Nuc. Adds Res.25:3389-3402, and Altschul et al. (1990) J. Mol. Biol. 215:403-410,respectively. Software for performing BLAST analyses is publiclyavailable through the National Center for Biotechnology Information. TheBLAST algorithm parameters W, T, and X determine the sensitivity andspeed of the alignment. The BLASTN program (for nucleotide sequences)uses as defaults a wordlength (W) of 11, an expectation (E) or 10, M=5,N=−4 and a comparison of both strands. For amino acid sequences, theBLASTP program uses as defaults a wordlength of 3, and expectation (E)of 10, and the BLOSUM62 scoring matrix (see Henikoff and Henikoff (1989)Proc. Natl. Acad. Sci. USA 89:10915) alignments (B) of 50, expectation(E) of 10, M=5, N=−4 and a comparison of both strands. The BLASTalgorithm is typically performed with the “low complexity” filter turnedoff.

The BLAST algorithm also performs a statistical analysis of thesimilarity between two sequences (see, e.g., Karlin and Altschul (1993)Proc. Natl. Acad. Sci. USA 90:5873-5787). One measure of similarityprovided by the BLAST algorithm is the smallest sum probability (P(N)),which provides an indication of the probability by which a match betweentwo nucleotide or amino acid sequences would occur by chance. Forexample, a nucleic acid is considered similar to a reference sequence ifthe smallest sum probability in a comparison of the test nucleic acid tothe reference nucleic acid is less than about 0.2, more preferably lessthan about 0.01, and most preferably less than about 0.001.

The phrase “selectively (or specifically) hybridizes to” refers to thebinding, duplexing, or hybridizing of a molecule only to a particularnucleotide sequence under stringent hybridization conditions when thatsequence is present in a complex mixture (including but not limited to,total cellular or library DNA or RNA).

The phrase “stringent hybridization conditions” refers to conditions oflow ionic strength and high temperature as is known in the art.Typically, under stringent conditions a probe will hybridize to itstarget subsequence in a complex mixture of nucleic acid (including butnot limited to, total cellular or library DNA or RNA) but does nothybridize to other sequences in the complex mixture. Stringentconditions are sequence-dependent and will be different in differentcircumstances. Longer sequences hybridize specifically at highertemperatures. An extensive guide to the hybridization of nucleic acidsis found in Tijssen, Techniques in Biochemistry and MolecularBiology—Hybridization with Nucleic Probes, “Overview of principles ofhybridization and the strategy of nucleic acid assays” (1993).Generally, stringent conditions are selected to be about 5-10° C. lowerthan the thermal melting point (T_(m)) for the specific sequence at adefined ionic strength pH. The T_(m) is the temperature (under definedionic strength, pH, and nucleic concentration) at which 50% of theprobes complementary to the target hybridize to the target sequence atequilibrium (as the target sequences are present in excess, at T_(m),50% of the probes are occupied at equilibrium). Stringent conditions maybe those in which the salt concentration is less than about 1.0 M sodiumion, typically about 0.01 to 1.0 M sodium ion concentration (or othersalts) at pH 7.0 to 8.3 and the temperature is at least about 30° C. forshort probes (including but not limited to, 10 to 50 nucleotides) and atleast about 60° C. for long probes (including but not limited to,greater than 50 nucleotides). Stringent conditions may also be achievedwith the addition of destabilizing agents such as formamide. Forselective or specific hybridization, a positive signal may be at leasttwo times background, optionally 10 times background hybridization.Exemplary stringent hybridization conditions can be as following: 50%formamide, 5×SSC, and 1% SDS, incubating at 42° C., or 5×SSC, 1% SDS,incubating at 65° C., with wash in 0.2×SSC, and 0.1% SDS at 65° C. Suchwashes can be performed for 5, 15, 30, 60, 120, or more minutes.

As used herein, the term “eukaryote” refers to organisms belonging tothe phylogenetic domain Eucarya such as animals (including but notlimited to, mammals, insects, reptiles, birds, etc.), ciliates, plants(including but not limited to, monocots, dicots, algae, etc.), fungi,yeasts, flagellates, microsporidia, protists, etc.

“Eukaryotic cell” and “eukaryotic cells” include by way of examplemammalian cells such as CHO, myeloma, BHK, immune cells, insect cells,avian cells, amphibian cells, e.g., frog oocytes, fungal and yeastcells. Yeast include by way of example Saccharomyces,Schizosaccharomyces, Hansenula, Candida, Torulopsis, Yarrowia, Pichia,et al. Particularly preferred yeast for expression includemethylotrophic yeast strains, e.g., Pichia pastoris, Hansenula,polymorpha, Pichia guillermordii, Pichia methanolica, Pichiainositovera, et al. (See e.g., U.S. Pat. Nos. 4,812,405, 4,818,700,4,929,555, 5,736,383, 5,955,349, 5,888,768, and 6,258,559, each of whichis hereby incorporated by reference for all purposes). These and otherpatents further describe promoters, terminators, enhancers, signalssequences, and other regulatory sequences useful for facilitatingheterologus gene expression in yeast, e.g., protein genes as in thepresent invention.

As used herein, the term “transformation” shall be used in a broad senseto refer to any introduction of DNA into a recipient host cell thatchanges the genotype and consequently results in a change in therecipient cell.

As used herein, the term “non-eukaryote” refers to non-eukaryoticorganisms. For example, a non-eukaryotic organism can belong to theEubacteria (including but not limited to, Escherichia coli, Thermusthermophilus, Bacillus stearothermophilus, etc.) phylogenetic domain, orthe Archaea (including but not limited to, Methanococcus jannaschii,Methanobacterium thermoautotrophicum, Halobacterium such as Haloferaxvolcanii and Halobacterium species NRC-1, Archaeoglobus fulgidus,Pyrococcus furiosus, Pyrococcus horikoshii, Aeuropyrum pernix, etc.)phylogenetic domain.

The term “subject” as used herein, refers to an animal, preferably amammal, most preferably a human, who is the object of treatment,observation or experiment.

DETAILED DESCRIPTION

One of skill in the art will be able to develop and use the same methodsgiven below, for the composition of feline erythropoietin and relatedmethods, for compositions and methods related to canine erythropoietin(cEPO) (SEQ ID NO: 31 mature amino acid sequence, SEQ ID NO: 30full-length amino acid sequence) and equine erythropoietin (eEPO) (SEQID NO: 33 mature amino acid sequence, SEQ ID NO: 32 full-length aminoacid sequence), for cEPO and eEPO with an unnatural, non-natural, and/ornon-naturally encoded amino acid incorporated into the cEPO and eEPOpolypeptides. These polypeptides may also be used as disclosed herein,for treatment of felines or other animals in need thereof, or they maybe used in the treatment of canines or equines. FIGS. 34 and 35 providecomparisons between each of the 166 amino acid sequences, for cEPO andeEPO, to fEPO (166 amino acids) which is discussed in greater detailherein, but the disclosure also provides support for the substitution,addition, or deletion of a non-naturally encoded amino acid to SEQ IDNO.s 31 and 33, cEPO and eEPO respectively.

I. Introduction

Feline EPO molecules comprising at least one unnatural amino acid areprovided in the invention. In certain embodiments of the invention, EPOwith at least one unnatural amino acid includes at least onepost-translational modification. In one embodiment, the at least onepost-translational modification comprises attachment of a molecule(including but not limited to, a dye, a polymer, including but notlimited to a derivative of polyethylene glycol, a photocrosslinker, acytotoxic compound, an affinity label, a derivative of biotin, a resin,a second protein or polypeptide, an antibody or antibody fragment, ametal chelator, a cofactor, a fatty acid, a carbohydrate, apolynucleotide (including but not limited to, DNA, RNA), etc.)comprising a second reactive group to the at least one unnatural aminoacid comprising a first reactive group utilizing chemistry methodologythat is known to one of ordinary skill in the art to be suitable for theparticular reactive groups. For example, the first reactive group is analkynyl moiety (including but not limited to, in the unnatural aminoacid p-propargyloxyphenylalanine, where the propargyl group is alsosometimes refer to as an acetylene moiety) and the second reactive groupis an azido moiety, and [3+2] cycloaddition chemistry methodologies areutilized. In another example, the first reactive group is the azidomoiety (including but not limited to, in the unnatural amino acidp-azido-L-phenylalanine) and the second reactive group is the alkynylmoiety. In certain embodiments of the modified fEPO of the presentinvention, at least one unnatural amino acid (including but not limitedto, unnatural amino acid containing a keto functional group) comprisingat least one post-translational modification, is used where the at leastone post-translational modification comprises a saccharide moiety. Incertain embodiments, the post-translational modification is made in vivoin a eukaryotic cell or in a non-eukaryotic cell.

In certain embodiments, the protein includes at least onepost-translational modification that is made in vivo by one host cell,where the post-translational modification is not normally made byanother host cell type. In certain embodiments, the protein includes atleast one post-translational modification that is made in vivo by aeukaryotic cell, where the post-translational modification is notnormally made by a non-eukaryotic cell. Examples of post-translationalmodifications include, but are not limited to, acetylation, acylation,lipid-modification, palmitoylation, palmitate addition, phosphorylation,glycolipid-linkage modification, and the like. In one embodiment, thepost-translational modification comprises attachment of anoligosaccharide to an asparagine by a GlcNAc-asparagine linkage(including but not limited to, where the oligosaccharide comprises(GlcNAc-Man)₂-Man-GlcNAc-GlcNAc, and the like). In another embodiment,the post-translational modification comprises attachment of anoligosaccharide (including but not limited to, Gal-GalNAc, Gal-GlcNAc,etc.) to a serine or threonine by a GalNAc-serine, a GalNAc-threonine, aGlcNAc-serine, or a GlcNAc-threonine linkage. In certain embodiments, aprotein or polypeptide of the invention can comprise a secretion orlocalization sequence, an epitope tag, a FLAG tag, a polyhistidine tag,a GST fusion, and/or the like.

The protein or polypeptide of interest can contain at least one, atleast two, at least three, at least four, at least five, at least six,at least seven, at least eight, at least nine, or ten or morenon-natural amino acids. The unnatural amino acids can be the same ordifferent, for example, there can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 ormore different sites in the protein that comprise 1, 2, 3, 4, 5, 6, 7,8, 9, 10 or more different unnatural amino acids. In certainembodiments, at least one, but fewer than all, of a particular aminoacid present in a naturally occurring version of the protein issubstituted with an unnatural amino acid.

The present invention provides methods and compositions based on membersof the GH supergene family, in particular fEPO, comprising at least onenon-naturally encoded amino acid. Introduction of at least onenon-naturally encoded amino acid into a GH supergene family member suchas fEPO can allow for the application of conjugation chemistries thatinvolve specific chemical reactions, including, but not limited to, withone or more non-naturally encoded amino acids while not reacting withthe commonly occurring 20 amino acids. In some embodiments, the GHsupergene family member such as fEPO comprising the non-naturallyencoded amino acid is linked to a water soluble polymer, such aspolyethylene glycol (PEG), via the side chain of the non-naturallyencoded amino acid. This invention provides a highly efficient methodfor the selective modification of proteins with PEG derivatives, whichinvolves the selective incorporation of non-genetically encoded aminoacids, including but not limited to, those amino acids containingfunctional groups or substituents not found in the 20 naturallyincorporated amino acids, including but not limited to an azide oracetylene moiety, into proteins in response to a selector codon and thesubsequent modification of those amino acids with a suitably reactivePEG derivative. Once incorporated, the amino acid side chains can thenbe modified by utilizing chemistry methodologies known to those ofordinary skill in the art to be suitable for the particular functionalgroups or substituents present in the naturally encoded amino acid.Known chemistry methodologies of a wide variety are suitable for use inthe present invention to incorporate a water soluble polymer into theprotein. Such methodologies include but are not limited to a Huisgen[3+2] cycloaddition reaction (see, e.g., Padwa, A. in ComprehensiveOrganic Synthesis, Vol. 4, (1991) Ed. Trost, B. M., Pergamon, Oxford, p.1069-1109; and, Huisgen, R. in 1,3-Dipolar Cycloaddition Chemistry,(1984) Ed. Padwa, A., Wiley, N.Y., p. 1-176) with, including but notlimited to, acetylene or azide derivatives, respectively.

Because the Huisgen [3+2] cycloaddition method involves a cycloadditionrather than a nucleophilic substitution reaction, proteins can bemodified with extremely high selectivity. The reaction can be carriedout at room temperature in aqueous conditions with excellentregioselectivity (1.4>1.5) by the addition of catalytic amounts of Cu(I)salts to the reaction mixture. See, e.g., Tornoe, et al., (2002) Org.Chem. 67:3057-3064; and, Rostovtsev, et al., (2002) Angew. Chem. Int.Ed. 41:2596-2599; and WO 03/101972. A molecule that can be added to aprotein of the invention through a [3+2] cycloaddition includesvirtually any molecule with a suitable functional group or substituentincluding but not limited to an azido or acetylene derivative. Thesemolecules can be added to an unnatural amino acid with an acetylenegroup, including but not limited to, p-prop argyloxyphenylalanine, orazido group, including but not limited to p-azido-phenylalanine,respectively.

The five-membered ring that results from the Huisgen [3+2] cycloadditionis not generally reversible in reducing environments and is stableagainst hydrolysis for extended periods in aqueous environments.Consequently, the physical and chemical characteristics of a widevariety of substances can be modified under demanding aqueous conditionswith the active PEG derivatives of the present invention. Even moreimportant, because the azide and acetylene moieties are specific for oneanother (and do not, for example, react with any of the 20 common,genetically-encoded amino acids), proteins can be modified in one ormore specific sites with extremely high selectivity.

The invention also provides water soluble and hydrolytically stablederivatives of PEG derivatives and related hydrophilic polymers havingone or more acetylene or azide moieties. The PEG polymer derivativesthat contain acetylene moieties are highly selective for coupling withazide moieties that have been introduced selectively into proteins inresponse to a selector codon. Similarly, PEG polymer derivatives thatcontain azide moieties are highly selective for coupling with acetylenemoieties that have been introduced selectively into proteins in responseto a selector codon.

More specifically, the azide moieties comprise, but are not limited to,alkyl azides, aryl azides and derivatives of these azides. Thederivatives of the alkyl and aryl azides can include other substituentsso long as the acetylene-specific reactivity is maintained. Theacetylene moieties comprise alkyl and aryl acetylenes and derivatives ofeach. The derivatives of the alkyl and aryl acetylenes can include othersubstituents so long as the azide-specific reactivity is maintained.

The present invention provides conjugates of substances having a widevariety of functional groups, substituents or moieties, with othersubstances including but not limited to water soluble polymers such asPEG, proteins, drugs, small molecules, biomaterials, or any otherdesirable compound or substance. The present invention also includesconjugates of substances having azide or acetylene moieties with PEGpolymer derivatives having the corresponding acetylene or azidemoieties. For example, a PEG polymer containing an azide moiety can becoupled to a biologically active molecule at a position in the proteinthat contains a non-genetically encoded amino acid bearing an acetylenefunctionality. The linkage by which the PEG and the biologically activemolecule are coupled includes but is not limited to the Huisgen [3+2]cycloaddition product.

It is well established in the art that PEG can be used to modify thesurfaces of biomaterials (see, e.g., U.S. Pat. No. 6,610,281; Mehvar,R., J. Pharmaceut. Sci., 3(1):125-136 (2000) which are incorporated byreference herein). The invention also includes biomaterials comprising asurface having one or more reactive azide or acetylene sites and one ormore of the azide- or acetylene-containing polymers of the inventioncoupled to the surface via the Huisgen [3+2] cycloaddition linkage.Biomaterials and other substances can also be coupled to the azide- oracetylene-activated polymer derivatives through a linkage other than theazide or acetylene linkage, such as through a linkage comprising acarboxylic acid, amine, alcohol or thiol moiety, to leave the azide oracetylene moiety available for subsequent reactions.

The invention includes a method of synthesizing the azide- and acetylenecontaining polymers of the invention. In the case of theazide-containing PEG derivative, the azide can be bonded directly to acarbon atom of the polymer. Alternatively, the azide-containing PEGderivative can be prepared by attaching a linking agent that has theazide moiety at one terminus to a conventional activated polymer so thatthe resulting polymer has the azide moiety at its terminus. In the caseof the acetylene-containing PEG derivative, the acetylene can be bondeddirectly to a carbon atom of the polymer. Alternatively, theacetylene-containing PEG derivative can be prepared by attaching alinking agent that has the acetylene moiety at one terminus to aconventional activated polymer so that the resulting polymer has theacetylene moiety at its terminus.

More specifically, in the case of the azide-containing PEG derivative, awater soluble polymer having at least one active hydroxyl moietyundergoes a reaction to produce a substituted polymer having a morereactive moiety, such as a mesylate, tresylate, tosylate or halogenleaving group, thereon. The preparation and use of PEG derivativescontaining sulfonyl acid halides, halogen atoms and other leaving groupsare well known to the skilled artisan. The resulting substituted polymerthen undergoes a reaction to substitute for the more reactive moiety anazide moiety at the terminus of the polymer. Alternatively, a watersoluble polymer having at least one active nucleophilic or electrophilicmoiety undergoes a reaction with a linking agent that has an azide atone terminus so that a covalent bond is fanned between the PEG polymerand the linking agent and the azide moiety is positioned at the terminusof the polymer. Nucleophilic and electrophilic moieties, includingamines, thiols, hydrazides, hydrazines, alcohols, carboxylates,aldehydes, ketones, thioesters and the like, are well known to theskilled artisan.

More specifically, in the case of the acetylene-containing PEGderivative, a water soluble polymer having at least one active hydroxylmoiety undergoes a reaction to displace a halogen or other activatedleaving group from a precursor that contains an acetylene moiety.Alternatively, a water soluble polymer having at least one activenucleophilic or electrophilic moiety undergoes a reaction with a linkingagent that has an acetylene at one terminus so that a covalent bond isformed between the PEG polymer and the linking agent and the acetylenemoiety is positioned at the terminus of the polymer. The use of halogenmoieties, activated leaving group, nucleophilic and electrophilicmoieties in the context of organic synthesis and the presparation anduse of PEG derivatives is well established to practitioners in the art.

The invention also provides a method for the selective modification ofproteins to add other substances to the modified protein, including butnot limited to water soluble polymers such as PEG and PEG derivativescontaining an azide or acetylene moiety. The azide- andacetylene-containing PEG derivatives can be used to modify theproperties of surfaces and molecules where biocompatibility, stability,solubility and lack of immunogenicity are important, while at the sametime providing a more selective means of attaching the PEG derivativesto proteins than was previously known in the art.

II. Growth Hormone Supergene Family

The following proteins include those encoded by genes of the growthhormone (GH) supergene family (Bazan, F., Immunology Today 11: 350-354(1991); Bazan, J. F. Science 257: 410-411 (1992); Mott, H. R. andCampbell, I. D., Current Opinion in Structural Biology 5: 114-121(1995); Silvennoinen, O. and Ihle, J. N., SIGNALLING BY THEHEMATOPOIETIC CYTOKINE RECEPTORS (1996)): growth hormone, prolactin,placental lactogen, erythropoietin (EPO), thrombopoietin (TPO),interleukin-2 (IL-2), IL-3, IL-4, IL-5, IL-6, IL-7, IL-9, IL-10, IL-11,IL-12 (p35 subunit), IL-13, IL-15, oncostatin M, ciliary neurotrophicfactor, leukemia inhibitory factor, alpha interferon, beta interferon,gamma interferon, omega interferon, tau interferon, granulocyte-colonystimulating factor (G-CSF), granulocyte-macrophage colony stimulatingfactor (GM-CSF), macrophage colony stimulating factor (M-CSF) andcardiotrophin-1 (CT-1) (“the GH supergene family”). It is anticipatedthat additional members of this gene family will be identified in thefuture through gene cloning and sequencing. Members of the GH supergenefamily have similar secondary and tertiary structures, despite the factthat they generally have limited amino acid or DNA sequence identity.The shared structural features allow new members of the gene family tobe readily identified. Given the extent of structural homology among themembers of the GH supergene family, non-naturally encoded amino acidsmay be incorporated into any members of the GH supergene family usingthe present invention.

Structures of a number of cytokines, including G-CSF (Hill, C. P., Proc.Natl. Acad. Sci. USA 90:5167-5171 (1993)), GM-CSF (Diederichs, K., etal. Science 154: 1779-1782 (1991); Walter et al., J. Mol. Biol.224:1075-1085 (1992)), IL-2 (Bazan, J. F. Science 257: 410-411 (1992);McKay, D. B. Science 257: 412 (1992)), IL-4 (Redfield et al.,Biochemistry 30: 11029-11035 (1991); Powers et al., Science256:1673-1677 (1992)), and IL-5 (Milburn et al., Nature 363: 172-176(1993)) have been determined by X-ray diffraction and NMR studies andshow striking conservation with the GH structure, despite a lack ofsignificant primary sequence homology. EPO is considered to be a memberof this family based upon modeling and mutagenesis studies (Boissel etal., J. Biol. Chem. 268: 15983-15993 (1993); Wen et al., J. Biol. Chem.269: 22839-22846 (1994)). A large number of additional cytokines andgrowth factors including ciliary neurotrophic factor (CNTF), leukemiainhibitory factor (LIF), thrombopoietin (TPO), oncostatin M, macrophagecolony stimulating factor (M-CSF), IL-3, IL-6, IL-7, IL-9, IL-12, IL-13,IL-15, and alpha, beta, omega, tau and gamma interferon belong to thisfamily (reviewed in Mott and Campbell, Current Opinion in StructuralBiology 5: 114-121 (1995); Silvennoinen and Ihle (1996) SIGNALLING BYTHE HEMATOPOIETIC CYTOKINE RECEPTORS). All of the above cytokines andgrowth factors are now considered to comprise one large gene family.

In addition to sharing similar secondary and tertiary structures,members of this family share the property that they must oligomerizecell surface receptors to activate intracellular signaling pathways.Some GH family members, including but not limited to; GH and EPO, bind asingle type of receptor and cause it to form homodimers. Other familymembers, including but not limited to, IL-2, IL4. and IL-6, bind morethan one type of receptor and cause the receptors to form heterodimersor higher order aggregates (Davis et al., (1993) Science 260: 1805-1808;Paonessa et al., 1995) EMBO J. 14: 1942-1951; Mott and Campbell, CurrentOpinion in Structural Biology 5: 114-121 (1995)). Mutagenesis studieshave shown that, like GH, these other cytokines and growth factorscontain multiple receptor binding sites, typically two, and bind theircognate receptors sequentially (Mott and Campbell, Current Opinion inStructural Biology 5: 114-121 (1995); Matthews et al., (1996) Proc.Natl. Acad. Sci. USA 93: 9471-9476). Like GH, the primary receptorbinding sites for these other family members occur primarily in the fouralpha helices and the A-B loop. The specific amino acids in the helicalbundles that participate in receptor binding differ amongst the familymembers. Most of the cell surface receptors that interact with membersof the GH supergene family are structurally related and comprise asecond large multi-gene family. See, e.g. U.S. Pat. No. 6,608,183.

A general conclusion reached from mutational studies of various membersof the GH supergene family is that the loops joining the alpha helicesgenerally tend to not be involved in receptor binding. In particular theshort B-C loop appears to be non-essential for receptor binding in most,if not all, family members. For this reason, the B-C loop may besubstituted with non-naturally encoded amino acids as described hereinin members of the GH supergene family. The A-B loop, the C-D loop (andD-E loop of interferon/ IL-10-like members of the GH superfamily) mayalso be substituted with a non-naturally-occurring amino acid. Aminoacids proximal to helix A and distal to the final helix also tend not tobe involved in receptor binding and also may be sites for introducingnon-naturally-occurring amino acids. In some embodiments, anon-naturally encoded amino acid is substituted at any position within aloop region, including but not limited to, the first 1, 2, 3, 4, 5, 6,7, or more amino acids of the A-B, B-C, C-D or D-E loop. In someembodiments, a non-naturally encoded amino acid is substituted withinthe last 1, 2, 3, 4, 5, 6, 7, or more amino acids of the A-B, B-C, C-Dor D-E loop.

Certain members of the GH family, including but not limited to, EPO,IL-2, IL-3, IL-4, IL-6, G-CSF, GM-CSF, TPO, IL-10, IL-12 p35, IL-13,IL-15 and beta-interferon contain N-linked and O-linked sugars. Theglycosylation sites in the proteins occur almost exclusively in the loopregions and not in the alpha helical bundles. Because the loop regionsgenerally are not involved in receptor binding and because they aresites for the covalent attachment of sugar groups, they may be usefulsites for introducing non-naturally-occurring amino acid substitutionsinto the proteins. Amino acids that comprise the N- and O-linkedglycosylation sites in the proteins may be sites fornon-naturally-occurring amino acid substitutions because these aminoacids are surface-exposed. Therefore, the natural protein can toleratebulky sugar groups attached to the proteins at these sites and theglycosylation sites tend to be located away from the receptor bindingsites.

Additional members of the GE gene family are likely to be discovered inthe future. New members of the GH supergene family can be identifiedthrough computer-aided secondary and tertiary structure analyses of thepredicted protein sequences. Members of the GH supergene familytypically possess four or five amphipathic helices joined by non-helicalamino acids (the loop regions). The proteins may contain a hydrophobicsignal sequence at their N-terminus to promote secretion from the cell.Such later discovered members of the GH supergen family also areincluded within this invention.

Reference to fEPO polypeptides in this application is intended to usefEPO as an example of a member of the GH supergene family. Thus, it isunderstood that the modifications and chemistries described herein withreference to fEPO can be equally applied to any other members of the GHsupergene family, including those specifically listed herein.

III. Expression System Producing Single or Multiple Gene Products ofInterest from a Single Expression Construct and Used with the PresentInvention

Described herein are novel expression systems for producing single ormultiple gene products of interest from a single expression construct orfrom multiple expression constructs. In one embodiment the presentinvention includes a eukaryotic suppression expression system in whichsuppressed protein genes of interest are transcribed from a singlevector encoding all elements necessary for suppression to include anartificial amino acid. In particular, the expression system contains avector capable of expressing proteins in eukaryotic host cells such thatthe said protein(s) contains an artificial amino acid. The expressionsystem contains a vector capable of expressing proteins in eukaryotichost cells such that the said protein(s) contains a non-natural aminoacid or unnatural amino acid. The expression system contains a vectorcapable of expressing proteins in eukaryotic host cells such that thesaid protein(s) contains a non-naturally encoded amino acid such as butnot limited to p-acetylphenylalanine (pAF). The expression vectors maycomprise the following elements operably linked: single or multiplecopies of a suppression tRNA sequence, including promoters andtranscription terminators operable in a eukaryotic cell; a promoterlinked to a DNA sequence encoding any gene of interest to be expressed(suppressed); and a promoter linked to a mammalian functional tRNAsynthetase coding region. An embodiment of the present invention aremammalian cells containing the suppression expression vector, and amethod of producing functional suppressed proteins in mammalian cellstransfected with the suppression expression vector.

This invention also pertains to the suppression expression of functionalproteins at adequate levels of expression via an expression system in aeukaryotic host cell. In one embodiment, the invention relates to thesuppression expression of functional proteins in eukaryotic cells,preferably mammalian cells, fungal or yeast cells and still morepreferably (Chinese Hamster Ovary) CHO cells, using a suppressionexpression system.

More specifically, one embodiment of the present invention relates tothe suppression expression of functional proteins in eukaryotic cells,for example mammalian cells, fungal or yeast cells using a suppressionexpression system wherein all suppression elements are contained on asingle vector. One embodiment of the present invention relates to thesuppression expression of functional proteins in (Chinese Hamster Ovary)CHO cells (ATCC banked cells, as well as known variants and cells and/orcell lines which those of skill in the art would know can be used inplace of CHO cells), using a suppression expression system wherein allsuppression elements are contained on a single vector. In one aspect ofthis embodiment of the invention, the suppression expression offunctional proteins in mammalian cells comprises using a suppressionexpression system comprising tRNA, tRNA synthetase, and protein ofinterest transcriptional/translationals elements.

Another embodiment of the invention provides the option of includingsingle or multiple tRNA elements in independent transcriptionalorientation to effectively modulate intracellular expression levels. Inanother embodiment, the invention provides the option of including asingle transcriptional unit which encodes a single protein of interestinto which the artificial amino acid is to be introduced. Anotherembodiment of the invention provides the option of including a multipletranscriptional units which encode multiple proteins of interest orsubunits of therein (such as antibody light and heavy chains) into whichthe artificial amino acid is to be introduced into either on or bothproteins.

Another embodiment of the invention is a eukaryotic cell line, such as aCHO cell line, that secretes the suppressed protein, wherein expressionof said protein is via the suppression expression system describedherein. In some embodiments, the eukaryotic cell is a CHO cell or ayeast cell, e.g., Pichia. Another embodiment of the invention is aculture of mammalian or yeast cells comprising a suppression expressionsystem capable of producing functional suppressed proteins. Vectorscontaining suppression expression sequences according to the inventionmay be introduced into the mammalian or yeast cells. During cellculturing, desired exogenous DNA sequences may be introduced to targetmammalian or yeast cells, such that exogenous DNA is inserted into thegenome of the mammalian or yeast cells randomly or via homologousrecombination. Depending upon the sequences employed, functionalsuppressed proteins may be recovered from the biomass of the cellculture or from the cell culture medium.

Yet another embodiment of the present invention is a method of producingfunctional suppressed proteins comprising culturing eukaryotic cells,preferably mammalian or yeast cells containing a suppression expressionsystem that expresses antibody light and heavy chain sequences, andrecovering functional antibodies from the cell culture. The functionalantibodies may be produced in batch fed cell cultures at levels suitablefor therapeutic use under conditions optimized for maximal commercialoutput. For example, CHO cells grown in batch fed cultures in whichglucose levels are continuously controlled can produce recombinantprotein for at least 12 days or more. See, for example, U.S. Pat. No.6,180,401 for a discussion relating to the output of recombinant proteinby cells grown in batch fed cultures.

A variety of different types of proteins may be expressed according tothe instant invention. Types of proteins include single polypeptides ormultiple assembled polypeptides such as but no limited to antibodies.For the purposes of this invention, numerous suppression expressionvector systems may be employed. For example, a suppression expressionvector may contain DNA elements which are derived from bacteria, suchas, but not limited to: E. coli, Bacillus, Salmonella; animal virusessuch as bovine papillomavirus virus, polyoma virus, adenovirus, vacciniavirus, baculovirus, retroviruses (RSV, MMTV or MOMLV) or SV40 virus.Additionally, cells which have integrated the suppression expresssionconstruct DNA into their chromosomes may be selected by introducing oneor more markers which allow selection of transfected host cells. Themarker may provide for any means known to those skilled in the art forselection, including but not limited to, prototrophy to an auxotrophichost, biocide resistance (e.g., antibiotics) or resistance to heavymetals such as copper. The selectable marker gene can either be directlylinked to the DNA sequences to be expressed, or introduced into the samecell by cotransformation. Additional elements that may be used inoptimizing synthesis of mRNA may include splice signals, as well astranscriptional promoters, enhancers, and termination signals.

More generally, once the vector or DNA sequence encoding the proteinsubunit has been prepared, the expression vector may be introduced intoan appropriate host cell. That is, the host cells may be transformed.Introduction of the plasmid into the host cell can be accomplished byvarious techniques well known to those of skill in the art. Theseinclude, but are not limited to, transfection (including electrophoresisand electroporation), protoplast fusion, calcium phosphateprecipitation, cell fusion with enveloped DNA, microinjection, PEI, andinfection with intact virus. See, Ridgway, A. A. G. “MammalianExpression Vectors” Chapter 24.2, pp. 470-472 Vectors, Rodriguez andDenhardt, Eds. (Butterworths, Boston, Mass. 1988). Most preferably, forstably integrated vectors, plasmid introduction into the host is viaelectroporation. The transformed cells are grown under conditionsappropriate to the production of the protein and assayed for proteinsynthesis. Exemplary assay techniques for identifying and quantifyinggene products of interest include enzyme-linked immunosorbent assay(ELISA), radioimmunoassay (RIA), or fluorescence-activated cell sorteranalysis (FACS), immunohistochemistry and the like.

In one embodiment of the present invention, the host cell line used forprotein expression is of mammalian origin. Those skilled in the art canreadily deter nine host cells or cell lines which would be suited forexpression of a desired gene product. Exemplary host cell lines include,but are not limited to, DG44 and DUXB11 (Chinese Hamster Ovary lines,DHFR minus), CHO-K1 derivatives, CHO-S, HELA (human cervical carcinoma),CVI (monkey kidney line), COS (a derivative of CVI with SV40 T antigen),R1610 (Chinese hamster fibroblast) BALBC/3T3 (mouse fibroblast), HAK(hamster kidney line), SP2/0 (mouse myeloma), P3.times.63-Ag3.653 (mousemyeloma), BFA-1c1BPT (bovine endothelial cells), RAJI (human lymphocyte)and 293 (human kidney). CHO cells are particularly preferred. Host cellsor cell lines are typically available from commercial services, theAmerican Tissue Culture Collection or from published literature.

In vitro production allows scale-up to give large amounts of the desiredpolypeptide produced using the suppression expression system. Techniquesfor eukaryotic, e.g., mammalian and yeast cell cultivation under tissueculture conditions are known in the art and include homogeneoussuspension culture, e.g. in an airlift reactor or in a continuousstirrer reactor, or immobilized or entrapped cell culture, e.g. inhollow fibers, microcapsules, on agarose microbeads or ceramiccartridges. For isolation and recovery of the antibodies, theimmunoglobulins in the culture supernatants may first be concentrated,e.g. by precipitation with ammonium sulphate, dialysis againsthygroscopic material such as PEG, filtration through selectivemembranes, or the like. If necessary and/or desired, the concentratedsolutions of multivalent antibodies are purified by the customarychromatography methods, for example gel filtration, ion-exchangechromatography, chromatography over DEAE-cellulose or (immuno-)affinitychromatography.

In one embodiment of the present invention, the eukaryotic cells usedfor expression are mammalian or yeast cells. In another embodiment ofthe present invention, the eukaryotic cells used for expression are CHOcells. In an additional embodiment of the present invention, theeukaryotic cells used for expression are other cells that can beefficiently cultured for high level protein production. As noted above,the obtaining or cloning of protein genes for incorporation intosuppression expression systems according to the invention is within thepurview of one of ordinary skill in the art. As noted, such proteingenes may encode mature genes, full-length proteins, or the genes may bemodified, e.g., by chimerization, humanization, domain deletion orsite-specific mutagenesis. Proteins produced by the system of thepresent invention include full-length proteins, mature proteins, cleavedproteins, uncleaved proteins, proteins disclosed herein, antibodies,antibody fragments including, but not limited to, Fv, Fc, Fab, and(Fab′)₂, single chain Fv (scFv), diabodies, triabodies, tetrabodies,bifunctional hybrid antibodies, CDR1, CDR2, CDR3, combinations of CDR's,variable regions, framework regions, constant regions, and the like.

In an embodiment of the present invention, the expression systemproduces proteins in eukaryotic cells, (non-limiting example; mammaliancells such as Chinese hamster ovary (CHO) cells, baby hamster kidney(BHK) cells, fibroblast cell lines and myeloma cells). In oneembodiment, CHO cells are employed as hosts for a suppression expressionsystem comprising a cistron comprising the following sequences: tRNAsequence gene, a eukaryotic promoter sequence that is functional in theparticular eukaryotic cell used for expression such as CMV, SV40 earlyor actin promoter sequences, preferably CMV; a DNA sequence encoding aprotein of interest, preferably at its 5′ end, a eukaryotic secretoryleader sequence; and flanked by a 5′ start and a 3′ stop codon, and apoly A sequence at its 3′ terminus.

In general, proteins suppressed and expressed according to the presentinvention may be used in any one of a number of conjugated (i.e. animmunoconjugate) or unconjugated forms. In particular, the proteins ofthe present invention may be conjugated to cytotoxins such asradioisotopes, therapeutic agents, cytostatic agents, biological toxinsor prodrugs. In particularly preferred embodiments, the proteinsproduced according to the expression system of the present invention maybe modified, such as by conjugation to radioisotopes or bioactivepeptides. Examples of radioisotopes useful according to the inventioninclude .sup.90Y, .sup.125I, .sup.131I, .sup.123I, .sup.111In,.sup.105Rh, .sup.153Sm, .sup.67Cu, .sup.67Ga, .sup.166Ho, .sup.177Lu,.sup.186Re and .sup.188Re, using anyone of a number of well knownchelators or direct labeling. In one embodiment, conjugated andunconjugated proteins may be used together in the same therapeuticregimen, e.g., as used in the currently approved therapeutic regimenemploying Zevalin for the treatment of certain non-Hodgkin's lymphomas.

In other embodiments, the proteins of the invention may be included incompositions that comprise modified proteins coupled to drugs, prodrugsor biological response modifiers such as methotrexate, adriamycine, andlymphokines such as interferon. Still other embodiments of the presentinvention comprise the use of modified proteins conjugated to specificbiotoxins such as ricin or diptheria toxin. In yet other embodiments themodified proteins may be complexed with other immunologically activeligands (e.g. antibodies or fragments thereof) wherein the resultingmolecule binds to a neoplastic cell and optionally an effector cell suchas a T cell. In yet other embodiments the modified proteins may becomplexed with other immunologically active ligands (e.g. antibodies orfragments thereof) wherein the resulting molecule binds to a neoplasticcell and an effector cell such as a T cell. The selection of whichconjugated and/or unconjugated modified protein to use will depend uponthe type and stage of cancer, use of adjunct treatment (e.g.,chemotherapy or external radiation) and patient condition. It will beappreciated that one skilled in the art could readily make such aselection in view of the teachings herein.

The invention is further illustrated by non-limiting Examples 2, 3, and4.

IV. General Recombinant Nucleic Acid Methods for Use with the Invention

In numerous embodiments of the present invention, nucleic acids encodinga fEPO of interest will be isolated, cloned and often altered usingrecombinant methods. Such embodiments are used, including but notlimited to, for protein expression or during the generation of variants,derivatives, expression cassettes, or other sequences derived from afEPO polypeptide. In some embodiments, the sequences encoding thepolypeptides of the invention are operably linked to a heterologouspromoter. Isolation of hEPO is described in, e.g., U.S. Pat. Nos.5,441,868; 5,547,933; 5,618,698; 5,621,080; and 6,544,748, andproduction of EPO in human cells is described in WO 93/09222, eachspecification herein incorporated by reference, and these techniques maybe applied by one of skill in the art to the isolation and production offEPO.

A nucleotide sequence encoding a fEPO polypeptide comprising anon-naturally encoded amino acid may be synthesized on the basis of theamino acid sequence of the parent polypeptide, including but not limitedto, having the amino acid sequence shown in SEQ ID NO: 2 (or SEQ ID NO:4, or alternate known sequences or SNPs, if desired), and then changingthe nucleotide sequence so as to effect introduction (i.e.,incorporation or substitution) or removal (i.e., deletion orsubstitution) of the relevant amino acid residue(s). The nucleotidesequence may be conveniently modified by site-directed mutagenesis inaccordance with conventional methods. Alternatively, the nucleotidesequence may be prepared by chemical synthesis, including but notlimited to, by using an oligonucleotide synthesizer, whereinoligonucleotides are designed based on the amino acid sequence of thedesired polypeptide, and preferably selecting those codons that arefavored in the host cell in which the recombinant polypeptide will beproduced. For example, several small oligonucleotides coding forportions of the desired polypeptide may be synthesized and assembled byPCR, ligation or ligation chain reaction. See, e.g., Barany, et al.,Proc. Natl. Acad. Sci. 88: 189-193 (1991); U.S. Pat. No. 6,521,427 whichare incorporated by reference herein.

This invention utilizes routine techniques in the field of recombinantgenetics. Basic texts disclosing the general methods of use in thisinvention include Sambrook et al., Molecular Cloning, A LaboratoryManual (3rd ed. 2001); Kriegler, Gene Transfer and Expression: ALaboratory Manual (1990); and Current Protocols in Molecular Biology(Ausubel et al., eds., 1994)).

General texts which describe molecular biological techniques includeBerger and Kimmel, Guide to Molecular Cloning Techniques, Methods inEnzymology volume 152 Academic Press, Inc., San Diego, Calif. (Berger);Sambrook et al., Molecular Cloning—A Laboratory Manual (2nd Ed.), Vol.1-3, Cold Spring Harbor Laboratory, Cold Spring Harbor, N.Y., 1989(“Sambrook”) and Current Protocols in Molecular Biology, F. M. Ausubelet al., eds., Current Protocols, a joint venture between GreenePublishing Associates, Inc. and John Wiley & Sons, Inc., (supplementedthrough 1999) (“Ausubel”)). These texts describe mutagenesis, the use ofvectors, promoters and many other relevant topics related to, includingbut not limited to, the generation of genes that include selector codonsfor production of proteins that include unnatural amino acids,orthogonal tRNAs, orthogonal synthetases, and pairs thereof.

Various types of mutagenesis are used in the invention for a variety ofpurposes, including but not limited to, to produce libraries of tRNAs,to produce libraries of synthetases, to produce selector codons, toinsert selector codons that encode unnatural amino acids in a protein orpolypeptide of interest. They include but are not limited tosite-directed, random point mutagenesis, homologous recombination, DNAshuffling or other recursive mutagenesis methods, chimeric construction,mutagenesis using uracil containing templates, oligonucleotide-directedmutagenesis, phosphorothioate-modified DNA mutagenesis, mutagenesisusing gapped duplex DNA or the like, or any combination thereof.Additional suitable methods include point mismatch repair, mutagenesisusing repair-deficient host strains, restriction-selection andrestriction-purification, deletion mutagenesis, mutagenesis by totalgene synthesis, double-strand break repair, and the like. Mutagenesis,including but not limited to, involving chimeric constructs, are alsoincluded in the present invention. In one embodiment, mutagenesis can beguided by known information of the naturally occurring molecule oraltered or mutated naturally occurring molecule, including but notlimited to, sequence, sequence comparisons, physical properties, crystalstructure or the like.

The texts and examples found herein describe these procedures.Additional information is found in the following publications andreferences cited within: Ling et al., Approaches to DNA mutagenesis: anoverview, Anal Biochem. 254(2): 157-178 (1997); Dale et al.,Oligonucleotide-directed random mutagenesis using the phosphorothioatemethod, Methods Mol. Biol. 57:369-374 (1996); Smith, In vitromutagenesis, Ann. Rev. Genet. 19:423-462(1985); Botstein & Shortle,Strategies and applications of in vitro mutagenesis, Science229:1193-1201(1985); Carter, Site-directed mutagenesis, Biochem. J.237:1-7 (1986); Kunkel, The efficiency of oligonucleotide directedmutagenesis, in Nucleic Acids & Molecular Biology (Eckstein, F. andLilley, D. M. J. eds., Springer Verlag, Berlin)) (1987); Kunkel, Rapidand efficient site-specific mutagenesis without phenotypic selection,Proc. Natl. Acad. Sci. USA 82:488-492 (1985); Kunkel et al., Rapid andefficient site-specific mutagenesis without phenotypic selection,Methods in Enzymol. 154, 367-382 (1987); Bass et al., Mutant Trprepressors with new DNA-binding specificities, Science 242:240-245(1988); Methods in Enzymol. 100: 468-500 (1983); Methods in Enzymol.154: 329-350 (1987); Zoller & Smith, Oligonucleotide-directedmutagenesis using M13-derived vectors: an efficient and generalprocedure for the production of point mutations in any DNA fragment,Nucleic Acids Res. 10:6487-6500 (1982); Zoller & Smith,Oligonucleotide-directed mutagenesis of DNA fragments cloned into M13vectors, Methods in Enzymol. 100:468-500 (1983); Zoller & Smith,Oligonucleotide-directed mutagenesis: a simple method using twooligonucleotide primers and a single-stranded DNA template, Methods inEnzymol. 154:329-350 (1987); Taylor et al., The use ofphosphorothioate-modified DNA in restriction enzyme reactions to preparenicked DNA, Nucl. Acids Res. 13: 8749-8764 (1985); Taylor et al., Therapid generation of oligonucleotide-directed mutations at high frequencyusing phosphorothioate-modified DNA, Nucl. Acids Res. 13: 8765-8787(1985); Nakamaye & Eckstein, Inhibition of restriction endonuclease NciI cleavage by phosphorothioate groups and its application tooligonucleotide-directed mutagenesis, Nucl. Acids Res. 14: 9679-9698(1986); Sayers et al., Y-T Exonucleases in phosphorothioate-basedoligonucleotide-directed mutagenesis, Nucl. Acids Res. 16:791-802(1988); Sayers et al., Strand specific cleavage ofphosphorothioate-containing DNA by reaction with restrictionendonucleases in the presence of ethidium bromide, (1988) Nucl. AcidsRes. 16: 803-814; Kramer et al., The gapped duplex DNA approach tooligonucleotide-directed mutation construction, Nucl. Acids Res. 12:9441-9456 (1984); Kramer & Fritz Oligonucleotide-directed constructionof mutations via gapped duplex DNA, Methods in Enzymol. 154:350-367(1987); Kramer et al., Improved enzymatic in vitro reactions in thegapped duplex DNA approach to oligonucleotide-directed construction ofmutations, Nucl. Acids Res. 16: 7207 (1988); Fritz et al.,Oligonucleotide-directed construction of mutations: a gapped duplex DNAprocedure without enzymatic reactions in vitro, Nucl. Acids Res. 16:6987-6999 (1988); Kramer et al., Point Mismatch Repair, Cell 38:879-887(1984); Carter et al., Improved oligonucleotide site-directedmutagenesis using M13 vectors, Nucl. Acids Res. 13: 4431-4443 (1985);Carter, Improved oligonucleotide-directed mutagenesis using M13 vectors,Methods in Enzymol. 154: 382-403 (1987); Eghtedarzadeh & Henikoff, Useof oligonucleotides to generate large deletions, Nucl. Acids Res. 14:5115 (1986); Wells et al., Importance of hydrogen-bond formation instabilizing the transition state of subtilisin, Phil. Trans. R. Soc.Lond. A 317: 415-423 (1986); Nambiar et al., Total synthesis and cloningof a gene coding for the ribonuclease S protein, Science 223: 1299-1301(1984); Sakamar and Khorana, Total synthesis and expression of a genefor the a-subunit of bovine rod outer segment guanine nucleotide-bindingprotein (transducin), Nucl. Acids Res. 14: 6361-6372 (1988); Wells etal., Cassette mutagenesis: an efficient method for generation ofmultiple mutations at defined sites, Gene 34:315-323 (1985); Grundströmet al., Oligonucleotide-directed mutagenesis by microscale ‘shot-gun’gene synthesis, Nucl. Acids Res. 13: 3305-3316 (1985); Mandecki,Oligonucleotide-directed double-strand break repair in plasmids ofEscherichia coli: a method for site-specific mutagenesis, Proc. Natl.Acad. Sci. USA, 83:7177-7181 (1986); Arnold, Protein engineering forunusual environments, Current Opinion in Biotechnology 4:450-455 (1993);Sieber, et al., Nature Biotechnology, 19:456-460 (2001). W. P. C.Stemmer, Nature 370, 389-91 (1994); and, I. A. Lorimer, I. Pastan,Nucleic Acids Res. 23, 3067-8 (1995). Additional details on many of theabove methods can be found in Methods in Enzymology Volume 154, whichalso describes useful controls for trouble-shooting problems withvarious mutagenesis methods.

The invention also relates to eukaryotic host cells, non-eukaryotic hostcells, and organisms for the in vivo incorporation of an unnatural aminoacid via orthogonal tRNA/RS pairs. Host cells are genetically engineered(including but not limited to, transformed, transduced or transfected)with the polynucleotides of the invention or constructs which include apolynucleotide of the invention, including but not limited to, a vectorof the invention, which can be, for example, a cloning vector or anexpression vector. The vector can be, for example, in the form of aplasmid, a bacterium, a virus, a naked polynucleotide, or a conjugatedpolynucleotide. The vectors are introduced into cells and/ormicroorganisms by standard methods including electroporation (From etal., Proc. Natl. Acad. Sci. USA 82, 5824 (1985), infection by viralvectors, high velocity ballistic penetration by small particles with thenucleic acid either within the matrix of small beads or particles, or onthe surface (Klein et al., Nature 327, 70-73 (1987)).

The engineered host cells can be cultured in conventional nutrient mediamodified as appropriate for such activities as, for example, screeningsteps, activating promoters or selecting transformants. These cells canoptionally be cultured into transgenic organisms. Other usefulreferences, including but not limited to for cell isolation and culture(e.g., for subsequent nucleic acid isolation) include Freshney (1994)Culture of Animal Cells, a Manual of Basic Technique, third edition,Wiley-Liss, New York and the references cited therein; Payne et al.(1992) Plant Cell and Tissue Culture in Liquid Systems John Wiley &Sons, Inc. New York, N.Y.; Gamborg and Phillips (eds) (1995) Plant Cell,Tissue and Organ Culture; Fundamental Methods Springer Lab Manual,Springer-Verlag (Berlin Heidelberg New York) and Atlas and Parks (eds)The Handbook of Microbiological Media (1993) CRC Press, Boca Raton, Fla.

Several well-known methods of introducing target nucleic acids intocells are available, any of which can be used in the invention. Theseinclude: fusion of the recipient cells with bacterial protoplastscontaining the DNA, electroporation, projectile bombardment, andinfection with viral vectors (discussed further, below), etc. Bacterialcells can be used to amplify the number of plasmids containing DNAconstructs of this invention. The bacteria are grown to log phase andthe plasmids within the bacteria can be isolated by a variety of methodsknown in the art (see, for instance, Sambrook). In addition, a plethoraof kits are commercially available for the purification of plasmids frombacteria, (see, e.g., EasyPrep™, FlexiPrep™, both from PharmaciaBiotech; StrataClean™, from Stratagene; and, QIAprep™ from Qiagen). Theisolated and purified plasmids are then further manipulated to produceother plasmids, used to transfect cells or incorporated into relatedvectors to infect organisms. Typical vectors contain transcription andtranslation terminators, transcription and translation initiationsequences, and promoters useful for regulation of the expression of theparticular target nucleic acid. The vectors optionally comprise genericexpression cassettes containing at least one independent terminatorsequence, sequences permitting replication of the cassette ineukaryotes, or prokaryotes, or both, (including but not limited to,shuttle vectors) and selection markers for both prokaryotic andeukaryotic systems. Vectors are suitable for replication and integrationin prokaryotes, eukaryotes, or preferably both. See, Giliman & Smith,Gene 8:81 (1979); Roberts, et al., Nature, 328:731 (1987); Schneider,B., et al., Protein Expr. Purif. 6435:10 (1995); Ausubel, Sambrook,Berger (all supra). A catalogue of Bacteria and Bacteriophages usefulfor cloning is provided, e.g., by the ATCC, e.g., The ATCC Catalogue ofBacteria and Bacteriophage (1992) Gherna et al. (eds) published by theATCC. Additional basic procedures for sequencing, cloning and otheraspects of molecular biology and underlying theoretical considerationsare also found in Watson et al. (1992) Recombinant DNA Second EditionScientific American Books, NY. In addition, essentially any nucleic acid(and virtually any labeled nucleic acid, whether standard ornon-standard) can be custom or standard ordered from any of a variety ofcommercial sources, such as the Midland Certified Reagent Company(Midland, Tex. mcrc.com), The Great American Gene Company (Ramona,Calif. available on the World Wide Web at genco.com), ExpressGen Inc.(Chicago, Ill. available on the World Wide Web at expressgen.com),Operon Technologies Inc. (Alameda, Calif.) and many others.

Selector Codons

Selector codons of the invention expand the genetic codon framework ofprotein biosynthetic machinery. For example, a selector codon includes,but is not limited to, a unique three base codon, a nonsense codon, suchas a stop codon, including but not limited to, an amber codon (UAG), oran opal codon (UGA), an unnatural codon, a four or more base codon, arare codon, or the like. It is readily apparent to those of ordinaryskill in the art that there is a wide range in the number of selectorcodons that can be introduced into a desired gene, including but notlimited to, one or more, two or more, more than three, 4, 5, 6, 7, 8, 9,10 or more in a single polynucleotide encoding at least a portion offEPO.

In one embodiment, the methods involve the use of a selector codon thatis a stop codon for the incorporation of unnatural amino acids in vivoin a eukaryotic cell. For example, an O-tRNA is produced that recognizesthe stop codon, including but not limited to, UAG, and is aminoacylatedby an O-RS with a desired unnatural amino acid. This O-tRNA is notrecognized by the naturally occurring host's aminoacyl-tRNA synthetases.Conventional site-directed mutagenesis can be used to introduce the stopcodon, including but not limited to, TAG, at the site of interest in apolypeptide of interest. See, e.g., Sayers, J. R., et al. (1988), 5′,3′Exonuclease in phosphorothioate-based oligonucleotide-directedmutagenesis. Nucleic Acids Res, 791-802. When the O-RS, O-tRNA and thenucleic acid that encodes the polypeptide of interest are combined invivo, the unnatural amino acid is incorporated in response to the UAGcodon to give a polypeptide containing the unnatural amino acid at thespecified position.

The incorporation of unnatural amino acids in vivo can be done withoutsignificant perturbation of the eukaryotic host cell. For example,because the suppression efficiency for the UAG codon depends upon thecompetition between the O-tRNA, including but not limited to, the ambersuppressor tRNA, and a eukaryotic release factor (including but notlimited to, eRF) (which binds to a stop codon and initiates release ofthe growing peptide from the ribosome), the suppression efficiency canbe modulated by, including but not limited to, increasing the expressionlevel of O-tRNA, and/or the suppressor tRNA.

Selector codons also comprise extended codons, including but not limitedto, four or more base codons, such as, four, five, six or more basecodons. Examples of four base codons include, including but not limitedto, AGGA, CUAG, UAGA, CCCU and the like. Examples of five base codonsinclude, but are not limited to, AGGAC, CCCCU, CCCUC, CUAGA, CUACU,UAGGC and the like. A feature of the invention includes using extendedcodons based on frameshift suppression. Four or more base codons caninsert, including but not limited to, one or multiple unnatural aminoacids into the same protein. For example, in the presence of mutatedO-tRNAs, including but not limited to, a special frameshift suppressortRNAs, with anticodon loops, for example, with at least 8-10 ntanticodon loops, the four or more base codon is read as single aminoacid. In other embodiments, the anticodon loops can decode, includingbut not limited to, at least a four-base codon, at least a five-basecodon, or at least a six-base codon or more. Since there are 256possible four-base codons, multiple unnatural amino acids can be encodedin the same cell using a four or more base codon. See, Anderson et al.,(2002) Exploring the Limits of Codon and Anticodon Size, Chemistry andBiology, 9:237-244; Magliery, (2001) Expanding the Genetic Code:Selection of Efficient Suppressors of Four-base Codons andIdentification of “Shifty” Four-base Codons with a Library Approach inEscherichia coli, J. Mol. Biol. 307: 755-769.

For example, four-base codons have been used to incorporate unnaturalamino acids into proteins using in vitro biosynthetic methods. See,e.g., Ma et al., (1993) Biochemistry, 32:7939; and Hohsaka et al.,(1999) J. Am. Chem. Soc., 121:34. CGGG and AGGU were used tosimultaneously incorporate 2-naphthylalanine and an NBD derivative oflysine into streptavidin in vitro with two chemically acylatedframeshift suppressor tRNAs. See, e.g., Hohsaka et al., (1999) J. Am.Chem. Soc., 121:12194. In an in vivo study, Moore et al. examined theability of tRNALeu derivatives with NCUA anticodons to suppress UAGNcodons (N can be U, A, G, or C), and found that the quadruplet UAGA canbe decoded by a tRNALeu with a UCUA anticodon with an efficiency of 13to 26% with little decoding in the 0 or −1 frame. See, Moore et al.,(2000) J. Mol. Biol., 298:195. In one embodiment, extended codons basedon rare codons or nonsense codons can be used in the present invention,which can reduce missense readthrough and frameshift suppression atother unwanted sites.

For a given system, a selector codon can also include one of the naturalthree base codons, where the endogenous system does not use (or rarelyuses) the natural base codon. For example, this includes a system thatis lacking a tRNA that recognizes the natural three base codon, and/or asystem where the three base codon is a rare codon.

Selector codons optionally include unnatural base pairs. These unnaturalbase pairs further expand the existing genetic alphabet. One extra basepair increases the number of triplet codons from 64 to 125. Propertiesof third base pairs include stable and selective base pairing, efficientenzymatic incorporation into DNA with high fidelity by a polymerase, andthe efficient continued primer extension after synthesis of the nascentunnatural base pair. Descriptions of unnatural base pairs which can beadapted for methods and compositions include, e.g., Hirao, et al.,(2002) An unnatural base pair for incorporating amino acid analoguesinto protein, Nature Biotechnology, 20:177-182. Other relevantpublications are listed below.

For in vivo usage, the unnatural nucleoside is membrane permeable and isphosphorylated to form the corresponding triphosphate. In addition, theincreased genetic information is stable and not destroyed by cellularenzymes. Previous efforts by Benner and others took advantage ofhydrogen bonding patterns that are different from those in canonicalWatson-Crick pairs, the most noteworthy example of which is theiso-C:iso-G pair. See, e.g., Switzer et al., (1989) J. Am. Chem. Soc.,111:8322; and Piccirilli et al., (1990) Nature, 343:33; Kool, (2000)Curr. Opin. Chem. Biol., 4:602. These bases in general mispair to somedegree with natural bases and cannot be enzymatically replicated. Kooland co-workers demonstrated that hydrophobic packing interactionsbetween bases can replace hydrogen bonding to drive the formation ofbase pair. See, Kool, (2000) Curr. Opin. Chem. Biol., 4:602; and Guckianand Kool, (1998) Angew. Chem. Int. Ed. Engl., 36, 2825. In an effort todevelop an unnatural base pair satisfying all the above requirements,Schultz, Romesberg and co-workers have systematically synthesized andstudied a series of unnatural hydrophobic bases. A PICS:PICS self-pairis found to be more stable than natural base pairs, and can beefficiently incorporated into DNA by Klenow fragment of Escherichia coliDNA polymerase I (KF). See, e.g., McMinn et al., (1999) J. Am. Chem.Soc., 121:11586; and Ogawa et al., (2000) J. Am. Chem. Soc., 122:3274. A3MN:3MN self-pair can be synthesized by KF with efficiency andselectivity sufficient for biological function. See, e.g., Ogawa et al.,(2000) J. Am. Chem. Soc., 122:8803. However, both bases act as a chainterminator for further replication. A mutant DNA polymerase has beenrecently evolved that can be used to replicate the PICS self pair. Inaddition, a 7AI self pair can be replicated. See, e.g., Tae et al.,(2001) J. Am. Chem. Soc., 123:7439. A novel metallobase pair, Dipic:Py,has also been developed, which forms a stable pair upon binding Cu(II).See, Meggers et al., (2000) J. Am. Chem. Soc., 122:10714. Becauseextended codons and unnatural codons are intrinsically orthogonal tonatural codons, the methods of the invention can take advantage of thisproperty to generate orthogonal tRNAs for them.

A translational bypassing system can also be used to incorporate anunnatural amino acid in a desired polypeptide. In a translationalbypassing system, a large sequence is incorporated into a gene but isnot translated into protein. The sequence contains a structure thatserves as a cue to induce the ribosome to hop over the sequence andresume translation downstream of the insertion.

In certain embodiments, the protein or polypeptide of interest (orportion thereof) in the methods and/or compositions of the invention isencoded by a nucleic acid. Typically, the nucleic acid comprises atleast one selector codon, at least two selector codons, at least threeselector codons, at least four selector codons, at least five selectorcodons, at least six selector codons, at least seven selector codons, atleast eight selector codons, at least nine selector codons, ten or moreselector codons.

Genes coding for proteins or polypeptides of interest can be mutagenizedusing methods well-known to one of skill in the art and described hereinunder “Mutagenesis and Other Molecular Biology Techniques” to include,for example, one or more selector codon for the incorporation of anunnatural amino acid. For example, a nucleic acid for a protein ofinterest is mutagenized to include one or more selector codon, providingfor the incorporation of the one or more unnatural amino acids. Theinvention includes any such variant, including but not limited to,mutant, versions of any protein, for example, including at least oneunnatural amino acid. Similarly, the invention also includescorresponding nucleic acids, i.e., any nucleic acid with one or moreselector codon that encodes one or more unnatural amino acid.

Nucleic acid molecules encoding a protein of interest such as fEPO maybe readily mutated to introduce a cysteine at any desired position ofthe polypeptide. Cysteine is widely used to introduce reactivemolecules, water soluble polymers, proteins, or a wide variety of othermolecules, onto a protein of interest. Methods suitable for theincorporation of cysteine into a desired position of the fEPOpolypeptide are well known in the art, such as those described in U.S.Pat. No. 6,608,183, which is incorporated by reference herein, andstandard mutagenesis techniques.

V. Non-Naturally Encoded Amino Acids

A very wide variety of non-naturally encoded amino acids are suitablefor use in the present invention. Any number of non-naturally encodedamino acids can be introduced into fEPO. In general, the introducednon-naturally encoded amino acids are substantially chemically inerttoward the 20 common, genetically-encoded amino acids (i.e., alanine,arginine, asparagine, aspartic acid, cysteine, glutamine, glutamic acid,glycine, histidine, isoleucine, leucine, lysine, methionine,phenylalanine, proline, serine, threonine, tryptophan, tyrosine, andvaline). In some embodiments, the non-naturally encoded amino acidsinclude side chain functional groups that react efficiently andselectively with functional groups not found in the 20 common aminoacids (including but not limited to, azido, ketone, aldehyde andaminooxy groups) to form stable conjugates. For example, a fEPOpolypeptide that includes a non-naturally encoded amino acid containingan azido functional group can be reacted with a polymer (including butnot limited to, poly(ethylene glycol) or, alternatively, a secondpolypeptide containing an alkyne moiety to form a stable conjugateresulting for the selective reaction of the azide and the alkynefunctional groups to form a Huisgen [3+2] cycloaddition product.

The generic structure of an alpha-amino acid is illustrated as follows:

A non-naturally encoded amino acid is typically any structure having theabove-listed formula wherein the R group is any substituent other thanone used in the twenty natural amino acids, and may be suitable for usein the present invention. Because the non-naturally encoded amino acidsof the invention typically differ from the natural amino acids only inthe structure of the side chain, the non-naturally encoded amino acidsform amide bonds with other amino acids, including but not limited to,natural or non-naturally encoded, in the same manner in which they areformed in naturally occurring polypeptides. However, the non-naturallyencoded amino acids have side chain groups that distinguish them fromthe natural amino acids. For example, R optionally comprises an alkyl-,aryl-, acyl-, keto-, azido, hydroxyl-, hydrazine, cyano-, halo-,hydrazide, alkenyl, alkynl, ether, thiol, seleno-, sulfonyl, borate,boronate, phospho, phosphono, phosphine, heterocyclic, enone, imine,aldehyde, ester, thioacid, hydroxylamine, amino group, or the like orany combination thereof Other non-naturally occurring amino acids ofinterest that may be suitable for use in the present invention include,but are not limited to, amino acids comprising a photoactivatablecross-linker, spin-labeled amino acids, fluorescent amino acids, metalbinding amino acids, metal-containing amino acids, radioactive aminoacids, amino acids with novel functional groups, amino acids thatcovalently or noncovalently interact with other molecules, photocagedand/or photoisomerizable amino acids, amino acids comprising biotin or abiotin analogue, glycosylated amino acids such as a sugar substitutedserine, other carbohydrate modified amino acids, keto-containing aminoacids, amino acids comprising polyethylene glycol or polyether, heavyatom substituted amino acids, chemically cleavable and/or photocleavableamino acids, amino acids with an elongated side chains as compared tonatural amino acids, including but not limited to, polyethers or longchain hydrocarbons, including but not limited to, greater than about 5or greater than about 10 carbons, carbon-linked sugar-containing aminoacids, redox-active amino acids, amino thioacid containing amino acids,and amino acids comprising one or more toxic moiety.

Exemplary non-naturally encoded amino acids that may be suitable for usein the present invention and that are useful for reactions with watersoluble polymers include, but are not limited to, those with carbonyl,aminooxy, hydroxylamine, hydrazide, semicarbazide, azide and alkynereactive groups. In some embodiments, non-naturally encoded amino acidscomprise a saccharide moiety. Examples of such amino acids includeN-acetyl-L-glucosaminyl-L-serine, N-acetyl-L-gal actosaminyl-L-serine,N-acetyl-L-glucosaminyl-L-threonine,N-acetyl-L-glucosaminyl-L-asparagine and O-mannosaminyl-L-serine.Examples of such amino acids also include examples where thenaturally-occuring N- or O-linkage between the amino acid and thesaccharide is replaced by a covalent linkage not commonly found innature—including but not limited to, an alkene, an oxime, a thioether,an amide and the like. Examples of such amino acids also includesaccharides that are not commonly found in naturally-occuring proteinssuch as 2-deoxy-glucose, 2-deoxygalactose and the like.

Many of the non-naturally encoded amino acids provided herein arecommercially available, e.g., from Sigma-Aldrich (St. Louis, Mo., USA),Novabiochem (a division of EMD Biosciences, Darmstadt, Germany), orPeptech (Burlington, Mass., USA). Those that are not commerciallyavailable are optionally synthesized as provided herein or usingstandard methods known to those of skill in the art. For organicsynthesis techniques, see, e.g., Organic Chemistry by Fessendon andFessendon, (1982, Second Edition, Willard Grant Press, Boston Mass.);Advanced Organic Chemistry by March (Third Edition, 1985, Wiley andSons, New York); and Advanced Organic Chemistry by Carey and Sundberg(Third Edition, Parts A and B, 1990, Plenum Press, New York). See, also,U.S. Patent Application Publications 2003/0082575 and 2003/0108885,incorporated by reference herein.

In addition to unnatural amino acids that contain novel side chains,unnatural amino acids that may be suitable for use in the presentinvention also optionally comprise modified backbone structures,including but not limited to, as illustrated by the structures ofFormula II and III:

wherein Z typically comprises OH, NH₂, SH, NH—R′, or S—R′; X and Y,which can be the same or different, typically comprise S or O, and R andR′, which are optionally the same or different, are typically selectedfrom the same list of constituents for the R group described above forthe unnatural amino acids having Formula I as well as hydrogen. Forexample, unnatural amino acids of the invention optionally comprisesubstitutions in the amino or carboxyl group as illustrated by FormulasII and III, Unnatural amino acids of this type include, but are notlimited to, α-hydroxy acids, α-thioacids α-aminothiocarboxylates,including but not limited to, with side chains corresponding to thecommon twenty natural amino acids or unnatural side chains. In addition,substitutions at the α-carbon optionally include, but are not limitedto, L, D, or α-α-disubstituted amino acids such as D-glutamate,D-alanine, D-methyl-O-tyrosine, aminobutyric acid, and the like. Otherstructural alternatives include cyclic amino acids, such as prolineanalogues as well as 3,4,6,7,8, and 9 membered ring proline analogues, βand γ amino acids such as substituted β-alanine and γ-amino butyricacid.

Many unnatural amino acids are based on natural amino acids, such astyrosine, glutamine, phenylalanine, and the like, and are suitable foruse in the present invention. Tyrosine analogs include, but are notlimited to, para-substituted tyrosines, ortho-substituted tyrosines, andmeta substituted tyrosines, where the substituted tyrosine comprises,including but not limited to, a keto group (including but not limitedto, an acetyl group), a benzoyl group, an amino group, a hydrazine, anhydroxyamine, a thiol group, a carboxy group, an isopropyl group, amethyl group, a C₆-C₂₀ straight chain or branched hydrocarbon, asaturated or unsaturated hydrocarbon, an O-methyl group, a polyethergroup, a nitro group, an alkynyl group or the like. In addition,multiply substituted aryl rings are also contemplated. Glutamine analogsthat may be suitable for use in the present invention include, but arenot limited to, α-hydroxy derivatives, γ-substituted derivatives, cyclicderivatives, and amide substituted glutamine derivatives. Examplephenylalanine analogs that may be suitable for use in the presentinvention include, but are not limited to, para-substitutedphenylalanines, ortho-substituted phenyalanines, and meta-substitutedphenylalanines, where the substituent comprises, including but notlimited to, a hydroxy group, a methoxy group, a methyl group, an allylgroup, an aldehyde, an azido, an iodo, a bromo, a keto group (includingbut not limited to, an acetyl group), a benzoyl, an alkynyl group, orthe like. Specific examples of unnatural amino acids that may besuitable for use in the present invention include, but are not limitedto, a p-acetyl-L-phenylalanine, a p-propargyloxyphenylalanine,O-methyl-L-tyrosine, an L-3-(2-naphthyl)alanine, a3-methyl-phenylalanine, an O-4-allyl-L-tyrosine, a 4-propyl-L-tyrosine,a tri-O-acetyl-GleNAcβ-serine, an L-Dopa, a fluorinated phenylalanine,an isopropyl-L-phenylalanine, a p-azido-L-phenylalanine, ap-acyl-L-phenylalanine, a p-benzoyl-L-phenylalanine, an L-phosphoserine,a phosphonoserine, a phosphonotyrosine, a p-iodo-phenylalanine, ap-bromophenylalanine, a p-amino-L-phenylalanine, and anisopropyl-L-phenylalanine, p-propargyloxy-phenylalanine, and the like.Examples of structures of a variety of unnatural amino acids that may besuitable for use in the present invention are provided in, for example,WO 2002/085923 entitled “In vivo incorporation of unnatural aminoacids.” See also Kiick et al., (2002) Incorporation of azides intorecombinant proteins for chemoselective modification by the Staudingerligtation, PNAS 99:19-24, for additional methionine analogs.

In one embodiment, compositions of fEPO that include an unnatural aminoacid (such as p-(propargyloxy)-phenyalanine) are provided. Variouscompositions comprising p-(propargyloxy)-phenyalanine and, including butnot limited to, proteins and/or cells, are also provided. In one aspect,a composition that includes the p-(propargyloxy)-phenyalanine unnaturalamino acid, further includes an orthogonal tRNA. The unnatural aminoacid can be bonded (including but not limited to, covalently) to theorthogonal tRNA, including but not limited to, covalently bonded to theorthogonal tRNA though an amino-acyl bond, covalently bonded to a 3′OHor a 2′OH of a terminal ribose sugar of the orthogonal tRNA, etc.

The chemical moieties via unnatural amino acids that can be incorporatedinto proteins offer a variety of advantages and manipulations of theprotein. For example, the unique reactivity of a keto functional groupallows selective modification of proteins with any of a number ofhydrazine- or hydroxylamine-containing reagents in vitro and in vivo. Aheavy atom unnatural amino acid, for example, can be useful for phasingx-ray structure data. The site-specific introduction of heavy atomsusing unnatural amino acids also provides selectivity and flexibility inchoosing positions for heavy atoms. Photoreactive unnatural amino acids(including but not limited to, amino acids with benzophenone andarylazides (including but not limited to, phenylazide) side chains), forexample, allow for efficient in vivo and in vitro photocrosslinking ofprotein. Examples of photoreactive unnatural amino acids include, butare not limited to, p-azido-phenylalanine and p-benzoyl-phenylalanine.The protein with the photoreactive unnatural amino acids can then becrosslinked at will by excitation of the photoreactive group-providingtemporal control. In one example, the methyl group of an unnatural aminocan be substituted with an isotopically labeled, including but notlimited to, methyl group, as a probe of local structure and dynamics,including but not limited to, with the use of nuclear magnetic resonanceand vibrational spectroscopy. Alkynyl or azido functional groups, forexample, allow the selective modification of proteins with moleculesthrough a [3+29 cyclo addition reaction.

Chemical Synthesis of Unnatural Amino Acids

Many of the unnatural amino acids suitable for use in the presentinvention are commercially available, e.g., from Sigma (USA) or Aldrich(Milwaukee, Wis., USA). Those that are not commercially available areoptionally synthesized as provided herein or as provided in variouspublications or using standard methods known to those of skill in theart. For organic synthesis techniques, see, e.g., Organic Chemistry byFessendon and Fessendon, (1982, Second Edition, Willard Grant Press,Boston Mass.); Advanced Organic Chemistry by March (Third Edition, 1985,Wiley and Sons, New York); and Advanced Organic Chemistry by Carey andSundberg (Third Edition, Parts A and B, 1990, Plenum Press, New York).Additional publications describing the synthesis of unnatural aminoacids include, e.g., WO 2002/085923 entitled “In vivo incorporation ofUnnatural Amino Acids;” Matsoukas et al., (1995) J. Med. Chem., 38,4660-4669; King, F. E. & Kidd, D. A. A. (1949) A New Synthesis ofGlutamine and of γ-Dipeptides of Glutamic Acid from PhthylatedIntermediates. J. Chem. Soc., 3315-3319; Friedman, O. M. & Chatterrji,R. (1959) Synthesis of Derivatives of Glutamine as Model Substrates forAnti-Tumor Agents. J. Am. Chem. Soc. 81, 3750-3752; Craig, J. C. et al.(1988) Absolute Configuration of the Enantiomers of 7-Chloro-4[[4-(diethylamino)-1-methylbutyl]amino]quinoline (Chloroquine). J. Org.Chem. 53, 1167-1170; Azoulay, M., Vilmont, M. & Frappier, F. (1991)Glutamine analogues as Potential Antimalarials, Eur. J. Med. Chem. 26,201-5; Koskinen, A. M. P. & Rapoport, H. (1989) Synthesis of4-Substituted Prolines as Conformationally Constrained Amino AcidAnalogues. J. Org. Chem. 54, 1859-1866; Christie, B. D. & Rapoport, H.(1985) Synthesis of Optically Pure Pipecolates from L-Asparagine.Application to the Total Synthesis of (+)-Apovincamine through AminoAcid Decarbonylation and Iminium Ion Cyclization. J. Org. Chem.1989:1859-1866; Barton et al., (1987) Synthesis of Novel a-Amino-Acidsand Derivatives Using Radical Chemistry: Synthesis of L-andD-a-Amino-Adipic Acids, L-a-aminopimelic Acid and AppropriateUnsaturated Derivatives. Tetrahedron Lett. 43:4297-4308; and, Subasingheet al., (1992) Quisqualic acid analogues: synthesis of beta-heterocyclic2-aminopropanoic acid derivatives and their activity at a novelquisqualate-sensitized site. J. Med. Chem. 35:4602-7. See also, patentapplication entitled “Protein Arrays,” attorney docket number P1001US00filed on Dec. 22, 2002.

A. Carbonyl Reactive Groups

Amino acids with a carbonyl reactive group allow for a variety ofreactions to link molecules (including but not limited to, PEG or otherwater soluble molecules) via nucleophilic addition or aldol condensationreactions among others.

Exemplary carbonyl-containing amino acids can be represented as follows:

wherein n is 0-10; R₁ is an alkyl, aryl, substituted alkyl, orsubstituted aryl; R₂ is H, alkyl, aryl, substituted alkyl, andsubstituted aryl; and R₃ is H, an amino acid, a polypeptide, or an aminoterminus modification group, and R₄ is H, an amino acid, a polypeptide,or a carboxy terminus modification group. In some embodiments, n is 1,R₁ is phenyl and R₂ is a simple alkyl (i.e., methyl, ethyl, or propyl)and the ketone moiety is positioned in the para position relative to thealkyl side chain. In some embodiments, n is 1, R₁ is phenyl and R₂ is asimple alkyl (i.e., methyl, ethyl, or propyl) and the ketone moiety ispositioned in the meta position relative to the alkyl side chain.

The synthesis of p-acetyl-(±)-phenylalanine andm-acetyl-(±)-phenylalanine is described in Zhang, Z., et al.,Biochemistry 42: 6735-6746 (2003), incorporated by reference. Othercarbonyl-containing amino acids can be similarly prepared by one skilledin the art.

In some embodiments, a polypeptide comprising a non-naturally encodedamino acid is chemically modified to generate a reactive carbonylfunctional group. For instance, an aldehyde functionality useful forconjugation reactions can be generated from a functionality havingadjacent amino and hydroxyl groups. Where the biologically activemolecule is a polypeptide, for example, an N-terminal serine orthreonine (which may be normally present or may be exposed via chemicalor enzymatic digestion) can be used to generate an aldehydefunctionality under mild oxidative cleavage conditions using periodate.See, e.g., Gaertner, et. al., Bioconjug. Chem. 3: 262-268 (1992);Geoghegan, K. & Stroh, J., Bioconjug. Chem. 3:138-146 (1992); Gaertneret al., J. Biol. Chem. 269:7224-7230 (1994). However, methods known inthe art are restricted to the amino acid at the N-terminus of thepeptide or protein.

In the present invention, a non-naturally encoded amino acid bearingadjacent hydroxyl and amino groups can be incorporated into thepolypeptide as a “masked” aldehyde functionality. For example,5-hydroxylysine bears a hydroxyl group adjacent to the epsilon amine.Reaction conditions for generating the aldehyde typically involveaddition of molar excess of sodium metaperiodate under mild conditionsto avoid oxidation at other sites within the polypeptide. The pH of theoxidation reaction is typically about 7.0. A typical reaction involvesthe addition of about 1.5 molar excess of sodium meta periodate to abuffered solution of the polypeptide, followed by incubation for about10 minutes in the dark. See, e.g. U.S. Pat. No. 6,423,685.

The carbonyl functionality can be reacted selectively with ahydrazine-hydrazide-, hydroxylamine-, or semicarbazide-containingreagent under mild conditions in aqueous solution to form thecorresponding hydrazone, oxime, or semicarbazone linkages, respectively,that are stable under physiological conditions. See, e.g., Jencks, W.P., J. Am. Chem. Soc. 81, 475-481 (1959); Shao, J. and Tam, J. P., J.Am. Chem. Soc. 117:3893-3899 (1995). Moreover, the unique reactivity ofthe carbonyl group allows for selective modification in the presence ofthe other amino acid side chains. See, e.g., Cornish, V. W., et al., J.Am. Chem. Soc. 118:8150-8151 (1996); Geoghegan, K. F. & Stroh, J. G.,Bioconjug. Chem. 3:138-146 (1992); Mahal, L. K., et al., Science276:1125-1128 (1997).

B. Hydrazine, Hydrazide or Semicarbazide Reactive Groups

Non-naturally encoded amino acids containing a nucleophilic group, suchas a hydrazine, hydrazide or semicarbazide, allow for reaction with avariety of electrophilic groups to form conjugates (including but notlimited to, with PEG or other water soluble polymers).

Exemplary hydrazine, hydrazide or semicarbazide-containing amino acidscan be represented as follows:

wherein n is 0-10; R₁ is an alkyl, aryl, substituted alkyl, orsubstituted aryl or not present; X, is O, N, or S or not present; R₂ isH, an amino acid, a polypeptide, or an amino terminus modificationgroup, and R₃ is H, an amino acid, a polypeptide, or a carboxy terminusmodification group.

In some embodiments, n is 4, R₁ is not present, and X is N. In someembodiments, n is 2, R₁ is not present, and X is not present. In someembodiments, n is 1, R₁ is phenyl, X is O, and the oxygen atom ispositioned para to the alphatic group on the aryl ring.

Hydrazide-, hydrazine-, and semicarbazide-containing amino acids areavailable from commercial sources. For instance, L-glutamate-γ-hydrazideis available from Sigma Chemical (St. Louis, Mo.). Other amino acids notavailable commercially can be prepared by one skilled in the art. See,e.g., U.S. Pat. No. 6,281,211.

Polypeptides containing non-naturally encoded amino acids that bearhydrazide, hydrazine or semicarbazide functionalities can be reactedefficiently and selectively with a variety of molecules that containaldehydes or other functional groups with similar chemical reactivity.See, e.g., Shao, J. and Tam, J., J. Am. Chem. Soc. 117:3893-3899 (1995).The unique reactivity of hydrazide, hydrazine and semicarbazidefunctional groups makes them significantly more reactive towardaldehydes, ketones and other electrophilic groups as compared to thenucleophilic groups present on the 20 common amino acids (including butnot limited to, the hydroxyl group of serine or threonine or the aminogroups of lysine and the N-terminus).

C. Aminooxy-Containing Amino Acids

Non-naturally encoded amino acids containing an aminooxy (also called ahydroxylamine) group allow for reaction with a variety of electrophilicgroups to form conjugates (including but not limited to, with PEG orother water soluble polymers). Like hydrazines, hydrazides andsemicarbazides, the enhanced nucleophilicity of the aminooxy grouppermits it to react efficiently and selectively with a variety ofmolecules that contain aldehydes or other functional groups with similarchemical reactivity. See, e.g., Shao, J. and Tam, J., J. Am. Chem. Soc.117:3893-3899 (1995); H. Hang and C. Bertozzi, Acc. Chem. Res. 34:727-736 (2001). Whereas the result of reaction with a hydrazine group isthe corresponding hydrazone, however, an oxime results generally fromthe reaction of an aminooxy group with a carbonyl-containing group suchas a ketone.

Exemplary amino acids containing aminooxy groups can be represented asfollows:

wherein n is 0-10; R1 is an alkyl, aryl, substituted alkyl, orsubstituted aryl or not present; X is O, N, S or not present; m is 0-10;Y═C(O) or not present; R₂ is H, an amino acid, a polypeptide, or anamino terminus modification group, and R₃ is H, an amino acid, apolypeptide, or a carboxy terminus modification group. In someembodiments, n is 1, R₁ is phenyl, X is O, m is 1, and Y is present. Insome embodiments, n is 2, R₁ and X are not present, m is 0, and Y is notpresent.

Aminooxy-containing amino acids can be prepared from readily availableamino acid precursors (homoserine, serine and threonine). See, e.g., M.Carrasco and R. Brown, J. Org. Chem. 68: 8853-8858 (2003). Certainaminooxy-containing amino acids, such as L-2-amino-4-(aminooxy)butyricacid), have been isolated from natural sources (Rosenthal, G. et al.,Life Sci. 60: 1635-1641 (1997). Other aminooxy-containing amino acidscan be prepared by one skilled in the art.

D. Azide and Alkyne Reactive Groups

The unique reactivity of azide and alkyne functional groups makes themextremely useful for the selective modification of polypeptides andother biological molecules. Organic azides, particularly alphaticazides, and alkynes are generally stable toward common reactive chemicalconditions. In particular, both the azide and the alkyne functionalgroups are inert toward the side chains (i.e., R groups) of the 20common amino acids found in naturally-occuring polypeptides. Whenbrought into close proximity, however, the “spring-loaded” nature of theazide and alkyne groups is revealed and they react selectively andefficiently via Huisgen [3+2] cycloaddition reaction to generate thecorresponding triazole. See, e.g., Chin J., et al., Science 301:964-7(2003); Wang, Q., et al., J. Am. Chem. Soc. 125, 3192-3193 (2003); Chin,J. W., et al., J. Am. Chem. Soc. 124:9026-9027 (2002).

Because the Huisgen cycloaddition reaction involves a selectivecycloaddition reaction (see, e.g., Padwa, A., in COMPREHENSIVE ORGANICSYNTHESIS, Vol. 4, (ed. Trost, B. M., 1991), p. 1069-1109; Huisgen, R.in 1,3-DIPOLAR CYCLOADDITION CHEMISTRY, (ed. Padwa, A., 1984), p. 1-176)rather than a nucleophilic substitution, the incorporation ofnon-naturally encoded amino acids bearing azide and alkyne-containingside chains permits the resultant polypeptides to be modifiedselectively at the position of the non-naturally encoded amino acid.Cycloaddition reaction involving azide or alkyne-containing fEPO can becarried out at room temperature under aqueous conditions by the additionof Cu(II) (including but not limited to, in the form of a catalyticamount of CuSO₄) in the presence of a reducing agent for reducing Cu(II)to Cu(I), in situ, in catalytic amount. See, e.g., Wang, Q., et al., J.Am. Chem. Soc. 125, 3192-3193 (2003); Tornoe, C. W., et al., J. Org.Chem. 67:3057-3064 (2002); Rostovtsev, et al., Angew. Chem. Int. Ed.41:2596-2599 (2002). Exemplary reducing agents include, including butnot limited to, ascorbate, metallic copper, quinine, hydroquinone,vitamin K, glutathione, cysteine, Fe²⁺, Co²⁺, and an applied electricpotential.

In some cases, where a Huisgen [3+2] cycloaddition reaction between anazide and an alkyne is desired, the fEPO polypeptide comprises anon-naturally encoded amino acid comprising an alkyne moiety and thewater soluble polymer to be attached to the amino acid comprises anazide moiety. Alternatively, the converse reaction (i.e., with the azidemoiety on the amino acid and the alkyne moiety present on the watersoluble polymer) can also be performed.

The azide functional group can also be reacted selectively with a watersoluble polymer containing an aryl ester and appropriatelyfunctionalized with an aryl phosphine moiety to generate an amidelinkage. The aryl phosphine group reduces the azide in situ and theresulting amine then reacts efficiently with a proximal ester linkage togenerate the corresponding amide. See, e.g., E. Saxon and C. Bertozzi,Science 287, 2007-2010 (2000). The azide-containing amino acid can beeither an alkyl azide (including but not limited to,2-amino-6-azido-1-hexanoic acid) or an aryl azide(p-azido-phenylalanine).

Exemplary water soluble polymers containing an aryl ester and aphosphine moiety can be represented as follows:

wherein X can be O, N, S or not present, Ph is phenyl, W is a watersoluble polymer and R can be H, alkyl, aryl, substituted alkyl andsubstituted aryl groups. Exemplary R groups include but are not limitedto —CH₂, —C(CH₃)₃, —OR′, —NR′R″, —SR′, -halogen, —C(O)R′, —CONR′R″,—S(O)₂R′, —S(O)₂NR′R″, —CN and —NO₂. R′, R″, R′″ and R″″ eachindependently refer to hydrogen, substituted or unsubstitutedheteroalkyl, substituted or unsubstituted aryl, including but notlimited to, aryl substituted with 1-3 halogens, substituted orunsubstituted alkyl, alkoxy or thioalkoxy groups, or arylalkyl groups.When a compound of the invention includes more than one R group, forexample, each of the R groups is independently selected as are each R′,R″, R′″ and R″″ groups when more than one of these groups is present.When R′ and R″ are attached to the same nitrogen atom, they can becombined with the nitrogen atom to form a 5-, 6-, or 7-membered ring.For example, —NR′R″ is meant to include, but not be limited to,1-pyrrolidinyl and 4-morpholinyl. From the above discussion ofsubstituents, one of skill in the art will understand that the term“alkyl” is meant to include groups including carbon atoms bound togroups other than hydrogen groups, such as haloalkyl (including but notlimited to, —CF₃ and —CH₂CF₃) and acyl (including but not limited to,—C(O)CH₃, —C(O)CF₃, —C(O)CH₂OCH₃, and the like).

The azide functional group can also be reacted selectively with a watersoluble polymer containing a thioester and appropriately functionalizedwith an aryl phosphine moiety to generate an amide linkage. The arylphosphine group reduces the azide in situ and the resulting amine thenreacts efficiently with the thioester linkage to generate thecorresponding amide. Exemplary water soluble polymers containing athioester and a phosphine moiety can be represented as follows:

wherein n is 1-10; X can be O, N, S or not present, Ph is phenyl, and Wis a water soluble polymer.

Exemplary alkyne-containing amino acids can be represented as follows:

wherein n is 0-10; R1 is an alkyl, aryl, substituted alkyl, orsubstituted aryl or not present; X is O, N, S or not present; m is 0-10,R₂ is H, an amino acid, a polypeptide, or an amino terminus modificationgroup, and R₃ is H, an amino acid, a polypeptide, or a carboxy terminusmodification group. In some embodiments, n is 1, R₁ is phenyl, X is notpresent, m is 0 and the acetylene moiety is positioned in the paraposition relative to the alkyl side chain. In some embodiments, n is 1,R₁ is phenyl, X is O, m is 1 and the propargyloxy group is positioned inthe para position relative to the alkyl side chain (i.e.,O-propargyl-tyrosine). In some embodiments, n is 1, R₁ and X are notpresent and m is 0 (i.e., proparylglycine).

Alkyne-containing amino acids are commercially available. For example,propargylglycine is commercially available from Peptech (Burlington,Mass.). Alternatively, alkyne-containing amino acids can be preparedaccording to standard methods. For instance, p-propargyloxyphenylalaninecan be synthesized, for example, as described in Deiters, A., et al., J.Am. Chem. Soc. 125: 11782-11783 (2003), and 4-alkynyl-L-phenylalaninecan be synthesized as described in Kayser, B., et al., Tetrahedron53(7): 2475-2484 (1997). Other alkyne-containing amino acids can beprepared by one skilled in the art.

Exemplary azide-containing amino acids can be represented as follows:

wherein n is 0-10; R₁ is an alkyl, aryl, substituted alkyl, substitutedaryl or not present; X is O, N, S or not present; in is 0-10; R₂ is H,an amino acid, a polypeptide, or an amino terminus modification group,and R₃ is H, an amino acid, a polypeptide, or a carboxy terminusmodification group. In some embodiments, n is 1, R₁ is phenyl, X is notpresent, m is 0 and the azide moiety is positioned para to the alkylside chain. In some embodiments, n is 0-4 and R₁ and X are not present,and m=0. In some embodiments, n is 1, R₁ is phenyl, X is O, m is 2 andthe β-azidoethoxy moiety is positioned in the para position relative tothe alkyl side chain.

Azide-containing amino acids are available from commercial sources. Forinstance, 4-azidophenylalanine can be obtained from Chem-ImpexInternational, Inc. (Wood Dale, Ill.). For those azide-containing aminoacids that are not commercially available, the azide group can beprepared relatively readily using standard methods known to those ofskill in the art, including but not limited to, via displacement of asuitable leaving group (including but not limited to, halide, mesylate,tosylate) or via opening of a suitably protected lactone. See, e.g.,Advanced Organic Chemistry by March (Third Edition, 1985, Wiley andSons, New York).

E. Aminothiol Reactive Groups

The unique reactivity of beta-substituted aminothiol functional groupsmakes them extremely useful for the selective modification ofpolypeptides and other biological molecules that contain aldehyde groupsvia formation of the thiazolidine. See, e.g., J. Shao and J. Tam, J. Am.Chem. Soc. 1995, 117 (14) 3893-3899. In some embodiments,beta-substituted aminothiol amino acids can be incorporated into fEPOpolypeptides and then reacted with water soluble polymers comprising analdehyde functionality. In some embodiments, a water soluble polymer,drug conjugate or other payload can be coupled to a fEPO polypeptidecomprising a beta-substituted aminothiol amino acid via formation of thethiazolidine.

Cellular Uptake of Unnatural Amino Acids

Unnatural amino acid uptake by a eukaryotic cell is one issue that istypically considered when designing and selecting unnatural amino acids,including but not limited to, for incorporation into a protein. Forexample, the high charge density of α-amino acids suggests that thesecompounds are unlikely to be cell permeable. Natural amino acids aretaken up into the eukaryotic cell via a collection of protein-basedtransport systems. A rapid screen can be done which assesses whichunnatural amino acids, if any, are taken up by cells. See, e.g., thetoxicity assays in, e.g., the application entitled “Protein Arrays,”attorney docket number P1001US00 filed on Dec. 22, 2002; and Liu, D. R.& Schultz, P. G. (1999) Progress toward the evolution of an organismwith an expanded genetic code. PNAS United States 96:4780-4785. Althoughuptake is easily analyzed with various assays, an alternative todesigning unnatural amino acids that are amenable to cellular uptakepathways is to provide biosynthetic pathways to create amino acids invivo.

Biosynthesis of Unnatural Amino Acids

Many biosynthetic pathways already exist in cells for the production ofamino acids and other compounds. While a biosynthetic method for aparticular unnatural amino acid may not exist in nature, including butnot limited to, in a eukaryotic cell, the invention provides suchmethods. For example, biosynthetic pathways for unnatural amino acidsare optionally generated in host cell by adding new enzymes or modifyingexisting host cell pathways. Additional new enzymes are optionallynaturally occurring enzymes or artificially evolved enzymes. Forexample, the biosynthesis of p-aminophenylalanine (as presented in anexample in WO 2002/085923 entitled “In vivo incorporation of unnaturalamino acids”) relies on the addition of a combination of known enzymesfrom other organisms. The genes for these enzymes can be introduced intoa eukaryotic cell by transforming the cell with a plasmid comprising thegenes. The genes, when expressed in the cell, provide an enzymaticpathway to synthesize the desired compound. Examples of the types ofenzymes that are optionally added are provided in the examples below.Additional enzymes sequences are found, for example, in Genbank.Artificially evolved enzymes are also optionally added into a cell inthe same manner. In this manner, the cellular machinery and resources ofa cell are manipulated to produce unnatural amino acids.

A variety of methods are available for producing novel enzymes for usein biosynthetic pathways or for evolution of existing pathways. Forexample, recursive recombination, including but not limited to, asdeveloped by Maxygen, Inc. (available on the world wide web atwww.maxygen.com), is optionally used to develop novel enzymes andpathways. See, e.g., Stemmer (1994), Rapid evolution of a protein invitro by DNA shuffling, Nature 370(4):389-391; and, Stemmer, (1994), DNAshuffling by random fragmentation and reassembly: In vitro recombinationfor molecular evolution, Proc. Natl. Acad. Sci. USA., 91:10747-10751.Similarly DesignPath™, developed by Genencor (available on the worldwide web at genencor.com) is optionally used for metabolic pathwayengineering, including but not limited to, to engineer a pathway tocreate O-methyl-L-trosine in a cell. This technology reconstructsexisting pathways in host organisms using a combination of new genes,including but not limited to, identified through functional genomics,and molecular evolution and design. Diversa Corporation (available onthe world wide web at diversa.com) also provides technology for rapidlyscreening libraries of genes and gene pathways, including but notlimited to, to create new pathways.

Typically, the unnatural amino acid produced with an engineeredbiosynthetic pathway of the invention is produced in a concentrationsufficient for efficient protein biosynthesis, including but not limitedto, a natural cellular amount, but not to such a degree as to affect theconcentration of the other amino acids or exhaust cellular resources.Typical concentrations produced in vivo in this manner are about 10 mMto about 0.05 mM. Once a cell is transformed with a plasmid comprisingthe genes used to produce enzymes desired for a specific pathway and anunnatural amino acid is generated, in vivo selections are optionallyused to further optimize the production of the unnatural amino acid forboth ribosomal protein synthesis and cell growth.

Polypeptides with Unnatural Amino Acids

The incorporation of an unnatural amino acid can be done for a varietyof purposes, including but not limited to, tailoring changes in proteinstructure and/or function, changing size, acidity, nucleophilicity,hydrogen bonding, hydrophobicity, accessibility of protease targetsites, targeting to a moiety (including but not limited to, for aprotein array), etc. Proteins that include an unnatural amino acid canhave enhanced or even entirely new catalytic or biophysical properties.For example, the following properties are optionally modified byinclusion of an unnatural amino acid into a protein: toxicity,biodistribution, structural properties, spectroscopic properties,chemical and/or photochemical properties, catalytic ability, half-life(including but not limited to, serum half-life), ability to react withother molecules, including but not limited to, covalently ornoncovalently, and the like. The compositions including proteins thatinclude at least one unnatural amino acid are useful for, including butnot limited to, novel therapeutics, diagnostics, catalytic enzymes,industrial enzymes, binding proteins (including but not limited to,antibodies), and including but not limited to, the study of proteinstructure and function. See, e.g., Dougherty, (2000) Unnatural AminoAcids as Probes of Protein Structure and Function, Current Opinion inChemical Biology, 4:645-652.

In one aspect of the invention, a composition includes at least oneprotein with at least one, including but not limited to, at least two,at least three, at least four, at least five, at least six, at leastseven, at least eight, at least nine, or at least ten or more unnaturalamino acids. The unnatural amino acids can be the same or different,including but not limited to, there can be 1, 2, 3, 4, 5, 6, 7, 8, 9, or10 or more different sites in the protein that comprise 1, 2, 3, 4, 5,6, 7, 8, 9, or 10 or more different unnatural amino acids. In anotheraspect, a composition includes a protein with at least one, but fewerthan all, of a particular amino acid present in the protein issubstituted with the unnatural amino acid. For a given protein with morethan one unnatural amino acids, the unnatural amino acids can beidentical or different (including but not limited to, the protein caninclude two or more different types of unnatural amino acids, or caninclude two of the same unnatural amino acid). For a given protein withmore than two unnatural amino acids, the unnatural amino acids can bethe same, different or a combination of a multiple unnatural amino acidof the same kind with at least one different unnatural amino acid.

Proteins or polypeptides of interest with at least one unnatural aminoacid are a feature of the invention. The invention also includespolypeptides or proteins with at least one unnatural amino acid producedusing the compositions and methods of the invention. An excipient(including but not limited to, a pharmaceutically acceptable excipient)can also be present with the protein.

By producing proteins or polypeptides of interest with at least oneunnatural amino acid in eukaryotic cells, proteins or polypeptides willtypically include eukaryotic posttranslational modifications. In certainembodiments, a protein includes at least one unnatural amino acid and atleast one post-translational modification that is made in vivo by aeukaryotic cell, where the post-translational modification is not madeby a prokaryotic cell. For example, the post-translation modificationincludes, including but not limited to, acetylation, acylation,lipid-modification, palmitoylation, palmitate addition, phosphorylation,glycolipid-linkage modification, glycosylation, and the like. In oneaspect, the post-translational modification includes attachment of anoligosaccharide (including but not limited to,(GlcNAc-Man)₂-Man-GlcNAc-GlcNAc)) to an asparagine by aGlcNAc-asparagine linkage. See also, Table 1, which lists some examplesof N-linked oligosaccharides of eukaryotic proteins (additional residuescan also be present, which are not shown). In another aspect, thepost-translational modification includes attachment of anoligosaccharide (including but not limited to, Gal-GalNAc, Gal-GlcNAc,etc.) to a serine or threonine by a GalNAc-serine or GalNAc-threoninelinkage, or a GlcNAc-serine or a GlcNAc-threonine linkage.

TABLE 1 EXAMPLES OF OLIGOSACCHARIDES THROUGH GlcNAc-LINKAGE

In yet another aspect, the post-translation modification includesproteolytic processing of precursors (including but not limited to,calcitonin precursor, calcitonin gene-related peptide precursor,preproparathyroid hormone, preproinsulin, proinsulin,prepro-opiomelanocortin, pro-opiomelanocortin and the like), assemblyinto a multisubunit protein or macromolecular assembly, translation toanother site in the cell (including but not limited to, to organelles,such as the endoplasmic reticulum, the golgi apparatus, the nucleus,lysosomes, peroxisomes, mitochondria, chloroplasts, vacuoles, etc., orthrough the secretory pathway). In certain embodiments, the proteincomprises a secretion or localization sequence, an epitope tag, a FLAGtag, a polyhistidine tag, a GST fusion, or the like.

One advantage of an unnatural amino acid is that it presents additionalchemical moieties that can be used to add additional molecules. Thesemodifications can be made in vivo in a eukaryotic or non-eukaryoticcell, or in vitro. Thus, in certain embodiments, the post-translationalmodification is through the unnatural amino acid. For example, thepost-translational modification can be through anucleophilic-electrophilic reaction. Most reactions currently used forthe selective modification of proteins involve covalent bond formationbetween nucleophilic and electrophilic reaction partners, including butnot limited to the reaction of α-haloketones with histidine or cysteineside chains. Selectivity in these cases is determined by the number andaccessibility of the nucleophilic residues in the protein. In proteinsof the invention, other more selective reactions can be used such as thereaction of an unnatural keto-amino acid with hydrazides or aminooxycompounds, in vitro and in vivo. See, e.g., Cornish, et al., (1996) Am.Chem. Soc., 118:8150-8151; Mahal, et al., (1997) Science, 276:1125-1128;Wang, et al., (2001) Science 292:498-500; Chin, et al., (2002) Am. Chem.Soc. 124:9026-9027; Chin, et al., (2002) Proc. Natl. Acad. Sci.,99:11020-11024; Wang, et al., (2003) Proc. Natl. Acad. Sci., 100:56-61;Zhang, et al., (2003) Biochemistry, 42:6735-6746; and, Chin, et al.,(2003) Science, in press. This allows the selective labeling ofvirtually any protein with a host of reagents including fluorophores,crosslinking agents, saccharide derivatives and cytotoxic molecules. Seealso, patent application Ser. No. 10/686,944, entitled “Glycoproteinsynthesis” filed Jan. 16, 2003, which is incorporated by referenceherein. Post-translational modifications, including but not limited to,through an azido amino acid, can also made through the Staudingerligation (including but not limited to, with triarylphosphine reagents).See, e.g., Kiick et al., (2002) Incorporation of azides into recombinantproteins for chemoselective modification by the Staudinger ligtation,PNAS 99:19-24.

This invention provides another highly efficient method for theselective modification of proteins, which involves the geneticincorporation of unnatural amino acids, including but not limited to,containing an azide or alkynyl moiety into proteins in response to aselector codon. These amino acid side chains can then be modified by,including but not limited to, a Huisgen [3+2] cycloaddition reaction(see, e.g., Padwa, A. in Comprehensive Organic Synthesis, Vol. 4, (1991)Ed. Trost, B. M., Pergamon, Oxford, p. 1069-1109; and, Huisgen, R. in1,3-Dipolar Cycloaddition Chemistry, (1984) Ed. Padwa, A., Wiley, NewYork, p. 1-176) with, including but not limited to, alkynyl or azidederivatives, respectively. Because this method involves a cycloadditionrather than a nucleophilic substitution, proteins can be modified withextremely high selectivity. This reaction can be carried out at roomtemperature in aqueous conditions with excellent regioselectivity(1.4>1.5) by the addition of catalytic amounts of Cu(I) salts to thereaction mixture. See, e.g., Tornoe, et al., (2002) Org. Chem.67:3057-3064; and, Rostovtsev, et al., (2002) Angew. Chem. Int. Ed.41:2596-2599. Another method that can be used is the ligand exchange ona bisarsenic compound with a tetracysteine motif, see, e.g., Griffin, etal., (1998) Science 281:269-272.

A molecule that can be added to a protein of the invention through a[3+29 cycloaddition includes virtually any molecule with an azido oralkynyl derivative. Molecules include, but are not limited to, dyes,fluorophores, crosslinking agents, saccharide derivatives, polymers(including but not limited to, derivatives of polyethylene glycol),photocrosslinkers, cytotoxic compounds, affinity labels, derivatives ofbiotin, resins, beads, a second protein or polypeptide (or more),polynucleotide(s) (including but not limited to, DNA, RNA, etc.), metalchelators, cofactors, fatty acids, carbohydrates, and the like. Thesemolecules can be added to an unnatural amino acid with an alkynyl group,including but not limited to, p-propargyloxyphenylalanine, or azidogroup, including but not limited to, p-azido-phenylalanine,respectively.

VI. In Vivo Generation of fEPO Comprising Non-Genetically-Encoded AminoAcids

The fEPO polypeptides of the invention can be generated in vivo usingmodified tRNA and tRNA synthetases to add to or substitute amino acidsthat are not encoded in naturally-occurring systems.

Methods for generating tRNAs and tRNA synthetases which use amino acidsthat are not encoded in naturally-occurring systems are described in,e.g., U.S. Patent Application Publications 2003/0082575 (Ser. No.10/126,927) and 2003/0108885 (Ser. No. 10/126,931), which areincorporated by reference herein. These methods involve generating atranslational machinery that functions independently of the synthetasesand tRNAs endogenous to the translation system (and are thereforesometimes referred to as “orthogonal”). Typically, the translationsystem comprises an orthogonal tRNA (O-tRNA) and an orthogonal aminoacyltRNA synthetase (O-RS). Typically, the O-RS preferentially aminoacylatesthe O-tRNA with at least one non-naturally occurring amino acid in thetranslation system and the O-tRNA recognizes at least one selector codonthat is not recognized by other tRNAs in the system. The translationsystem thus inserts the non-naturally-encoded amino acid into a proteinproduced in the system, in response to an encoded selector codon,thereby “substituting” an amino acid into a position in the encodedpolypeptide.

A wide variety of orthogonal tRNAs and aminoacyl tRNA synthetases havebeen described in the art for inserting particular synthetic amino acidsinto polypeptides, and are generally suitable for ise in the presentinvention. For example, keto-specific O-tRNA/aminoacyl-tRNA synthetasesare described in Wang, L., et al., Proc. Natl. Acad. Sci. USA 100:56-61(2003) and Zhang, Z. et al., Biochem. 42(22):6735-6746 (2003). ExemplaryO-RS, or portions thereof, are encoded by polynucleotide sequences andinclude amino acid sequences disclosed in U.S. Patent ApplicationPublications 2003/0082575 (Ser. No. 10/126,927) and 2003/0108885 (Ser.No. 10/126,931), which are incorporated by reference herein.Corresponding O-tRNA molecules for use with the O-RSs are also describedin U.S. Patent Application Publications 2003/0082575 (Ser. No.10/126,927) and 2003/0108885 (Ser. No. 10/126,931), which areincorporated by reference herein.

An example of an azide-specific O-tRNA/aminoacyl-tRNA synthetase systemis described in Chin, J. W., et al., J. Am. Chem. Soc. 124:9026-9027(2002). Exemplary O-RS sequences for p-azido-L-Phe include, but are notlimited to, nucleotide sequences SEQ ID NOs: 14-16 and 29-32 and aminoacid sequences SEQ ID NOs: 46-48 and 61-64 as disclosed in U.S. PatentApplication Publication 2003/0108885 (Ser. No. 10/126,931), which isincorporated by reference herein. Exemplary O-tRNA sequences suitablefor use in the present invention include, but are not limited to,nucleotide sequences SEQ ID NOs: 1-3 as disclosed in U.S. PatentApplication Publication 2003/0082575 (Ser. No. 10/126,927) which isincorporated by reference herein. Other examples ofO-tRNA/aminoacyl-tRNA synthetase pairs specific to particularnon-naturally encoded amino acids are described in U.S. PatentApplication Publication 2003/0082575 (Ser. No. 10/126,927) which isincorporated by reference herein. O-RS and O-tRNA that incorporate bothketo- and azide-containing amino acids in S. cerevisiae are described inChin, J. W., et al., Science 301:964-967 (2003).

Use of O-tRNA/aminoacyl-tRNA synthetases involves selection of aspecific codon which encodes the non-naturally encoded amino acid. Whileany codon can be used, it is generally desirable to select a codon thatis rarely or never used in the cell in which the O-tRNA/aminoacyl-tRNAsynthetase is expressed. For example, exemplary codons include nonsensecodon such as stop codons (amber, ochre, and opal), four or more basecodons and other natural three-base codons that are rarely or unused.

Specific selector codon(s) can be introduced into appropriate positionsin the fEPO polynucleotide coding sequence using mutagenesis methodsknown in the art (including but not limited to, site-specificmutagenesis, cassette mutagenesis, restriction selection mutagenesis,etc.).

Methods for generating components of the protein biosynthetic machinery,such as O-RSs, O-tRNAs, and orthogonal O-tRNA/O-RS pairs that can beused to incorporate a non-naturally encoded amino acid are described inWang, L., et al., Science 292: 498-500 (2001); Chin, J. W., et al., J.Am. Chem. Soc. 124:9026-9027 (2002); Zhang, Z. et al., Biochemistry 42:6735-6746 (2003). Methods and compositions for the in vivo incorporationof non-naturally encoded amino acids are described in U.S. PatentApplication Publication 2003/0082575 (Ser. No. 10/126,927) which isincorporated by reference herein. Methods for selecting an orthogonaltRNA-tRNA synthetase pair for use in in vivo translation system of anorganism are also described in U.S. Patent Application Publications2003/0082575 (Ser. No. 10/126,927) and 2003/0108885 (Ser. No.10/126,931), which are incorporated by reference herein.

Methods for producing at least one recombinant orthogonal aminoacyl-tRNAsynthetase (O-RS) comprise: (a) generating a library of (optionallymutant) RSs derived from at least one aminoacyl-tRNA synthetase (RS)from a first organism, including but not limited to, a prokaryoticorganism, such as Methanococcus jannaschii, Methanobacteriumthermoautotrophicum, Halobacterium, Escherichia coli, A. fulgidus, P.furiosus, P. horikoshii, A. pernix, T. thermophilus, or the like, or aeukaryotic organism; (b) selecting (and/or screening) the library of RSs(optionally mutant RSs) for members that aminoacylate an orthogonal tRNA(O-tRNA) in the presence of a non-naturally encoded amino acid and anatural amino acid, thereby providing a pool of active (optionallymutant) RSs; and/or, (c) selecting (optionally through negativeselection) the pool for active RSs (including but not limited to, mutantRSs) that preferentially aminoacylate the O-tRNA in the absence of thenon-naturally encoded amino acid, thereby providing the at least onerecombinant O-RS; wherein the at least one recombinant O-RSpreferentially aminoacylates the O-tRNA with the non-naturally encodedamino acid.

In one embodiment, the RS is an inactive RS. The inactive RS can begenerated by mutating an active RS. For example, the inactive RS can begenerated by mutating at least about 1, at least about 2, at least about3, at least about 4, at least about 5, at least about 6, or at leastabout 10 or more amino acids to different amino acids, including but notlimited to, alanine.

Libraries of mutant RSs can be generated using various techniques knownin the art, including but not limited to rational design based onprotein three dimensional RS structure, or mutagenesis of RS nucleotidesin a random or rational design technique. For example, the mutant RSscan be generated by site-specific mutations, random mutations, diversitygenerating recombination mutations, chimeric constructs, rational designand by other methods described herein or known in the art.

In one embodiment, selecting (and/or screening) the library of RSs(optionally mutant RSs) for members that are active, including but notlimited to, that aminoacylate an orthogonal tRNA (O-tRNA) in thepresence of a non-naturally encoded amino acid and a natural amino acid,includes: introducing a positive selection or screening marker,including but not limited to, an antibiotic resistance gene, or thelike, and the library of (optionally mutant) RSs into a plurality ofcells, wherein the positive selection and/or screening marker comprisesat least one selector codon, including but not limited to, an amber,ochre, or opal codon; growing the plurality of cells in the presence ofa selection agent; identifying cells that survive (or show a specificresponse) in the presence of the selection and/or screening agent bysuppressing the at least one selector codon in the positive selection orscreening marker, thereby providing a subset of positively selectedcells that contains the pool of active (optionally mutant) RSs.Optionally, the selection and/or screening agent concentration can bevaried.

In one aspect, the positive selection marker is a chloramphenicolacetyltransferase (CAT) gene and the selector codon is an amber stopcodon in the CAT gene. Optionally, the positive selection marker is aβ-lactamase gene and the selector codon is an amber stop codon in theβ-lactamase gene. In another aspect the positive screening markercomprises a fluorescent or luminescent screening marker or an affinitybased screening marker (including but not limited to, a cell surfacemarker).

In one embodiment, negatively selecting or screening the pool for activeRSs (optionally mutants) that preferentially aminoacylate the O-tRNA inthe absence of the non-naturally encoded amino acid includes:introducing a negative selection or screening marker with the pool ofactive (optionally mutant) RSs from the positive selection or screeninginto a plurality of cells of a second organism, wherein the negativeselection or screening marker comprises at least one selector codon(including but not limited to, an antibiotic resistance gene, includingbut not limited to, a chloramphenicol acetyltransferase (CAT) gene);and, identifying cells that survive or show a specific screeningresponse in a first medium supplemented with the non-naturally encodedamino acid and a screening or selection agent, but fail to survive or toshow the specific response in a second medium not supplemented with thenon-naturally encoded amino acid and the selection or screening agent,thereby providing surviving cells or screened cells with the at leastone recombinant O-RS. For example, a CAT identification protocoloptionally acts as a positive selection and/or a negative screening indetermination of appropriate O-RS recombinants. For instance, a pool ofclones is optionally replicated on growth plates containing CAT (whichcomprises at least one selector codon) either with or without one ormore non-naturally encoded amino acid. Colonies growing exclusively onthe plates containing non-naturally encoded amino acids are thusregarded as containing recombinant O-RS. In one aspect, theconcentration of the selection (and/or screening) agent is varied. Insome aspects the first and second organisms are different. Thus, thefirst and/or second organism optionally comprises: a prokaryote, aeukaryote, a mammal, an Escherichia coli, a fungus, a yeast, anarchaebacterium, a eubacterium, a plant, an insect, a protist, etc. Inother embodiments, the screening marker comprises a fluorescent orluminescent screening marker or an affinity based screening marker.

In another embodiment, screening or selecting (including but not limitedto, negatively selecting) the pool for active (optionally mutant) RSsincludes: isolating the pool of active mutant RSs from the positiveselection step (b); introducing a negative selection or screeningmarker, wherein the negative selection or screening marker comprises atleast one selector codon (including but not limited to, a toxic markergene, including but not limited to, a ribonuclease barnase gene,comprising at least one selector codon), and the pool of active(optionally mutant) RSs into a plurality of cells of a second organism;and identifying cells that survive or show a specific screening responsein a first medium not supplemented with the non-naturally encoded aminoacid, but fail to survive or show a specific screening response in asecond medium supplemented with the non-naturally encoded amino acid,thereby providing surviving or screened cells with the at least onerecombinant O-RS, wherein the at least one recombinant O-RS is specificfor the non-naturally encoded amino acid. In one aspect, the at leastone selector codon comprises about two or more selector codons. Suchembodiments optionally can include wherein the at least one selectorcodon comprises two or more selector codons, and wherein the first andsecond organism are different (including but not limited to, eachorganism is optionally, including but not limited to, a prokaryote, aeukaryote, a mammal, an Escherichia call, a fungi, a yeast, anarchaebacteria, a eubacteria, a plant, an insect, a protist, etc.).Also, some aspects include wherein the negative selection markercomprises a ribonuclease barnase gene (which comprises at least oneselector codon). Other aspects include wherein the screening markeroptionally comprises a fluorescent or luminescent screening marker or anaffinity based screening marker. In the embodiments herein, thescreenings and/or selections optionally include variation of thescreening and/or selection stringency.

In one embodiment, the methods for producing at least one recombinantorthogonal aminoacyl-tRNA synthetase (O-RS) can further comprise: (d)isolating the at least one recombinant O-RS; (e) generating a second setof O-RS (optionally mutated) derived from the at least one recombinantO-RS; and, (f) repeating steps (b) and (c) until a mutated O-RS isobtained that comprises an ability to preferentially aminoacylate theO-tRNA. Optionally, steps (d)-(f) are repeated, including but notlimited to, at least about two times. In one aspect, the second set ofmutated O-RS derived from at least one recombinant O-RS can be generatedby mutagenesis, including but not limited to, random mutagenesis,site-specific mutagenesis, recombination or a combination thereof.

The stringency of the selection/screening steps, including but notlimited to, the positive selection/screening step (b), the negativeselection/screening step (c) or both the positive and negativeselection/screening steps (b) and (c), in the above-described methods,optionally includes varying the selection/screening stringency. Inanother embodiment, the positive selection/screening step (b), thenegative selection/screening step (c) or both the positive and negativeselection/screening steps (b) and (c) comprise using a reporter, whereinthe reporter is detected by fluorescence-activated cell sorting (FACS)or wherein the reporter is detected by luminescence. Optionally, thereporter is displayed on a cell surface, on a phage display or the likeand selected based upon affinity or catalytic activity involving thenon-naturally encoded amino acid or an analogue. In one embodiment, themutated synthetase is displayed on a cell surface, on a phage display orthe like.

Methods for producing a recombinant orthogonal tRNA (O-tRNA) include:(a) generating a library of mutant tRNAs derived from at least one tRNA,including but not limited to, a suppressor tRNA, from a first organism;(b) selecting (including but not limited to, negatively selecting) orscreening the library for (optionally mutant) tRNAs that areaminoacylated by an aminoacyl-tRNA synthetase (RS) from a secondorganism in the absence of a RS from the first organism, therebyproviding a pool of tRNAs (optionally mutant); and, (c) selecting orscreening the pool of tRNAs (optionally mutant) for members that areaminoacylated by an introduced orthogonal RS (O-RS), thereby providingat least one recombinant O-tRNA; wherein the at least one recombinantO-tRNA recognizes a selector codon and is not efficiency recognized bythe RS from the second organism and is preferentially aminoacylated bythe O-RS. In some embodiments the at least one tRNA is a suppressor tRNAand/or comprises a unique three base codon of natural and/or unnaturalbases, or is a nonsense codon, a rare codon, an unnatural codon, a codoncomprising at least 4 bases, an amber codon, an ochre codon, or an opalstop codon. In one embodiment, the recombinant O-tRNA possesses animprovement of orthogonality. It will be appreciated that in someembodiments, O-tRNA is optionally imported into a first organism from asecond organism without the need for modification. In variousembodiments, the first and second organisms are either the same ordifferent and are optionally chosen from, including but not limited to,prokaryotes (including but not limited to, Methanococcus jannaschii,Methanobacteium thermoautotrophicum, Escherichia coli, Halobacterium,etc.), eukaryotes, mammals, fungi, yeasts, archaebacteria, eubacteria,plants, insects, protists, etc. Additionally, the recombinant tRNA isoptionally aminoacylated by a non-naturally encoded amino acid, whereinthe non-naturally encoded amino acid is biosynthesized in vivo eithernaturally or through genetic manipulation. The non-naturally encodedamino acid is optionally added to a growth medium for at least the firstor second organism.

In one aspect, selecting (including but not limited to, negativelyselecting) or screening the library for (optionally mutant) tRNAs thatare aminoacylated by an aminoacyl-tRNA synthetase (step (b)) includes:introducing a toxic marker gene, wherein the toxic marker gene comprisesat least one of the selector codons (or a gene that leads to theproduction of a toxic or static agent or a gene essential to theorganism wherein such marker gene comprises at least one selector codon)and the library of (optionally mutant) tRNAs into a plurality of cellsfrom the second organism; and, selecting surviving cells, wherein thesurviving cells contain the pool of (optionally mutant) tRNAs comprisingat least one orthogonal tRNA or nonfunctional tRNA. For example,surviving cells can be selected by using a comparison ratio cell densityassay.

In another aspect, the toxic marker gene can include two or moreselector codons. In another embodiment of the methods, the toxic markergene is a ribonuclease barnase gene, where the ribonuclease barnase genecomprises at least one amber codon. Optionally, the ribonuclease barnasegene can include two or more amber codons.

In one embodiment, selecting or screening the pool of (optionallymutant) tRNAs for members that are aminoacylated by an introducedorthogonal RS (O-RS) can include: introducing a positive selection orscreening marker gene, wherein the positive marker gene comprises a drugresistance gene (including but not limited to, β-lactamase gene,comprising at least one of the selector codons, such as at least oneamber stop codon) or a gene essential to the organism, or a gene thatleads to detoxification of a toxic agent, along with the O-RS, and thepool of (optionally mutant) tRNAs into a plurality of cells from thesecond organism; and, identifying surviving or screened cells grown inthe presence of a selection or screening agent, including but notlimited to, an antibiotic, thereby providing a pool of cells possessingthe at least one recombinant tRNA, where the at least recombinant tRNAis aminoacylated by the O-RS and inserts an amino acid into atranslation product encoded by the positive marker gene, in response tothe at least one selector codons. In another embodiment, theconcentration of the selection and/or screening agent is varied.

Methods for generating specific O-tRNA/O-RS pairs are provided. Methodsinclude: (a) generating a library of mutant tRNAs derived from at leastone tRNA from a first organism; (b) negatively selecting or screeningthe library for (optionally mutan) tRNAs that are aminoacylated by anaminoacyl-tRNA synthetase (RS) from a second organism in the absence ofa RS from the first organism, thereby providing a pool of (optionallymutant) tRNAs; (c) selecting or screening the pool of (optionallymutant) tRNAs for members that are aminoacylated by an introducedorthogonal RS (O-RS), thereby providing at least one recombinant O-tRNA.The at least one recombinant O-tRNA recognizes a selector codon and isnot efficiency recognized by the RS from the second organism and ispreferentially aminoacylated by the O-RS. The method also includes (d)generating a library of (optionally mutant) RSs derived from at leastone aminoacyl-tRNA synthetase (RS) from a third organism; (e) selectingor screening the library of mutant RSs for members that preferentiallyaminoacylate the at least one recombinant O-tRNA in the presence of anon-naturally encoded amino acid and a natural amino acid, therebyproviding a pool of active (optionally mutant) RSs; and, (f) negativelyselecting or screening the pool for active (optionally mutant) RSs thatpreferentially aminoacylate the at least one recombinant O-tRNA in theabsence of the non-naturally encoded amino acid, thereby providing theat least one specific O-tRNA/O-RS pair, wherein the at least onespecific O-tRNA/O-RS pair comprises at least one recombinant O-RS thatis specific for the non-naturally encoded amino acid and the at leastone recombinant O-tRNA. Specific O-tRNA/O-RS pairs produced by themethods are included. For example, the specific O-tRNA/O-RS pair caninclude, including but not limited to, a mutRNATyr-mutTyrRS pair, suchas a mutRNATyr-SS12TyrRS pair, a mutRNALeu-mutLeuRS pair, amutRNAThr-mutThrRS pair, a mutRNAGlu-mutGluRS pair, or the like.Additionally, such methods include wherein the first and third organismare the same (including but not limited to, Methanococcus jannaschii).

Methods for selecting an orthogonal tRNA-tRNA synthetase pair for use inan in vivo translation system of a second organism are also included inthe present invention. The methods include: introducing a marker gene, atRNA and an aminoacyl-tRNA synthetase (RS) isolated or derived from afirst organism into a first set of cells from the second organism;introducing the marker gene and the tRNA into a duplicate cell set froma second organism; and, selecting for surviving cells in the first setthat fail to survive in the duplicate cell set or screening for cellsshowing a specific screening response that fail to give such response inthe duplicate cell set, wherein the first set and the duplicate cell setare grown in the presence of a selection or screening agent, wherein thesurviving or screened cells comprise the orthogonal tRNA-tRNA synthetasepair for use in the in the in vivo translation system of the secondorganism. In one embodiment, comparing and selecting or screeningincludes an in vivo complementation assay. The concentration of theselection or screening agent can be varied.

The organisms of the present invention comprise a variety of organismand a variety of combinations. For example, the first and the secondorganisms of the methods of the present invention can be the same ordifferent. In one embodiment, the organisms are optionally a prokaryoticorganism, including but not limited to, Methanococcus jannaschii,Methanobacterium thermoautotrophicum, Halobacterium, Escherichia coil,A. fulgidus, P. furiosus, P. horikoshii, A. pernix, T. thermophilus, orthe like. Alternatively, the organisms optionally comprise a eukaryoticorganism, including but not limited to, plants (including but notlimited to, complex plants such as mono cots, or dicots), algae,protists, fungi (including but not limited to, yeast, etc), animals(including but not limited to, mammals, insects, arthropods, etc.), orthe like. In another embodiment, the second organism is a prokaryoticorganism, including but not limited to, Methanococcus jannaschii,Methanobacterium thermoautotrophicum, Halobacterium, Escherichia coil,A. fulgidus, Halobacterium, P. furiosus, P. horikoshii, A. pernix, T.thermophilus, or the like. Alternatively, the second organism can be aeukaryotic organism, including but not limited to, a yeast, a animalcell, a plant cell, a fungus, a mammalian cell, or the like. In variousembodiments the first and second organisms are different.

VII. Location of Non-Naturally-Occurring Amino Acids in fEPO

The present invention contemplates incorporation of one or morenon-naturally-occurring amino acids into fEPO. One or morenon-naturally-occurring amino acids may be incorporated at a particularposition which does not disrupt activity of the polypeptide. This can beachieved by making “conservative” substitutions, including but notlimited to, substituting hydrophobic amino acids with hydrophobic aminoacids, bulky amino acids for bulky amino acids, hydrophilic amino acidsfor hydrophilic amino acids) and/or inserting thenon-naturally-occurring amino acid in a location that is not requiredfor activity.

Regions of fEPO can be illustrated as follows, wherein the amino acidpositions in fEPO are indicated in the middle row:

A variety of biochemical and structural approaches can be employed toselect the desired sites for substitution with a non-naturally encodedamino acid within the fEPO polypeptide. It is readily apparent to thoseof ordinary skill in the art that any position of the polypeptide chainis suitable for selection to incorporate a non-naturally encoded aminoacid, and selection may be based on rational design or by randomselection for any or no particular desired purpose. Selection of desiredsites may be for producing an fEPO molecule having any desired propertyor activity, including but not limited to agonists, super-agonists,inverse agonists, antagonists, receptor binding modulators, receptoractivity modulators, dimer or multimer formation, no change to activityor property compared to the native molecule, or manipulating anyphysical or chemical property of the polypeptide such as solubility,aggregation, or stability. For example, locations in the polypeptiderequired for biological activity of fEPO can be identified using alaninescanning or homolog scanning methods known in the art. See, e.g.,Bittorf, T. et al. FEBS, 336:133-136 (1993) (identifying criticalresidues for EPO activity), Wen, D., et al. JBC, 269:22839-22846 (1994)(alanine scanning mutagenesis employed to identify functionallyimportant domains of hEPO), and Elliot, S. et al. Blood, 89:493-502(1997) (identifying key electrostatic interactions between hEPO andhuman EPO receptor). Residues other than those identified as critical tobiological activity by alanine or homolog scanning mutagenesis may begood candidates for substitution with a non-naturally encoded amino aciddepending on the desired activity sought for the polypeptide.Alternatively, the sites identified as critical to biological activitymay also be good candidates for substitution with a non-naturallyencoded amino acid, again depending on the desired activity sought forthe polypeptide. Another alternative would be to simply make serialsubstitutions in each position on the polypeptide chain with anon-naturally encoded amino acid and observe the effect on theactivities of the polypeptide. It is readily apparent to those ofordinary skill in the art that any means, technique, or method forselecting a position for substitution with a non-natural amino acid intoany polypeptide is suitable for use in the present invention.

The structure and activity of naturally-occurring mutants of fEPO thatcontain deletions can also be examined to determine regions of theprotein that are likely to be tolerant of substitution with anon-naturally encoded amino acid. See, e.g., Bittorf et al., FEBS,336:133 (1993); Wen et al, JBC, 269:22839 (1994). Once residues that arelikely to be intolerant to substitution with non-naturally encoded aminoacids have been eliminated, the impact of proposed substitutions at eachof the remaining positions can be examined from the three-dimensionalstructure of fEPO and its binding proteins. See Syed et al., Nature,395: 511 (1998) and Cheetham et al., Nature Structural Biology, 5:861(1998); x-ray crystallographic and NMR structures of hEPO are availablein the Protein Data Bank (PDB, www.rcsb.org with PDB ID's: 1CN4, LEER,and 1BUY), a centralized database containing three-dimensionalstructural data of large molecules of proteins and nucleic acids. Thus,by using the known information regarding hEPO, those of skill in the artcan readily identify amino acid positions in fEPO (see FIG. 1) that canbe substituted with non-naturally encoded amino acids.

In some embodiments, the EPO polypeptides of the invention comprise oneor more non-naturally occurring amino acid positioned in a region of theprotein that does not disrupt the helices or beta sheet secondarystructure of EPO. In some embodiments, the one or more non-naturallyencoded amino acid are incorporated or substituted in one or more of thefollowing regions corresponding to secondary structures in EPO asfollows: 1-7 (N-terminus), 8-26 (A helix), 27-38 (region between A helixand B helix), 39-41 (Beta sheet 1), 42-46 (region between Beta sheet 1and mini helix B′), 47-52 (mini B′ helix), 53-54 (region between mini B′helix and B helix), 55-83 (B helix), 84-89 (region between B helix and Chelix), 90-113 (C helix), 114-121 (mini C′ helix), 122-132 (regionbetween mini C′ helix and Beta sheet 2), 133-135 (Beta sheet 2), 136-137(region between Beta sheet 2 and D helix), 138-161 (D helix), 162-166(C-terminus). In some embodiments, the one or more non-naturally encodedamino acids are incorporated in one of the following positions in EPO:1, 2, 3, 4, 5, 6, 8, 9, 17, 21, 24, 25, 26, 27, 28, 30, 31, 32, 34, 35,36, 37, 38, 39, 40, 43, 45, 47, 50, 51, 52, 53, 54, 55, 56, 57, 58, 68,72, 76, 77, 78, 79, 80, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 107,110, 111, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124,125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 136, 154, 157, 158,159, 160, 162, 163, 164, 165 and 166. In some embodiments, the EPOpolypeptides of the invention comprise one or more non-naturallyoccurring amino acids at one or more of the following positions: 21, 24,27, 28, 30, 31, 36, 37, 38, 55, 72, 83, 85, 86, 87, 89, 113, 116, 119,120, 121, 123, 124, 125, 126, 127, 128, 129, 130, and 162. In someembodiments, the non-naturally occurring amino acid at these or otherpositions are linked to a water soluble molecule, including but notlimited to positions 21, 24, 38, 83, 85, 86, 89, 116, 119, 121, 124,125, 126, 127, and 128.

Exemplary sites of incorporation of a non-naturally encoded amino acidinclude, but are not limited to, those that are excluded from Site I andSite II, may be fully or partially solvent exposed, have minimal or nohydrogen-bonding interactions with nearby residues, may be minimallyexposed to nearby reactive residues, and may be in regions that arehighly flexible (including but not limited to, C-D loop) or structurallyrigid (including but not limited to, B helix) as predicted by thethree-dimensional crystal structure of hEPO with its receptor.

A wide variety of non-naturally encoded amino acids can be substitutedfor, or incorporated into, a given position in fEPO. In general, aparticular non-naturally encoded amino acid is selected forincorporation based on an examination of the three dimensional crystalstructure of fEPO with its receptor, a preference for conservativesubstitutions (i.e., aryl-based non-naturally encoded amino acids, suchas p-acetylphenylalanine or O-propargyhyrosine substituting for Phe, Tyror Trp), and the specific conjugation chemistry that one desires tointroduce into the fEPO polypeptide (including but not limited to, theintroduction of 4-azidophenylalanine if one wants to effect a Huisgen[3+2] cycloaddition with a water soluble polymer bearing an alkynemoiety or a amide bond formation with a water soluble polymer that bearsan aryl ester that, in turn, incorporates a phosphine moiety).

In one embodiment, the method further includes incorporating into theprotein the unnatural amino acid, where the unnatural amino acidcomprises a first reactive group; and contacting the protein with amolecule (including but not limited to, a dye, a polymer, including butnot limited to, a derivative of polyethylene glycol, a photocrosslinker,a cytotoxic compound, an affinity label, a derivative of biotin, aresin, a second protein or polypeptide, a metal chelator, a cofactor, afatty acid, a carbohydrate, a polynucleotide (including but not limitedto, DNA, RNA, etc.), etc.) that comprises a second reactive group. Thefirst reactive group reacts with the second reactive group to attach themolecule to the unnatural amino acid through a [3+29 cycloaddition. Inone embodiment, the first reactive group is an alkynyl or azido moietyand the second reactive group is an azido or alkynyl moiety. Forexample, the first reactive group is the alkynyl moiety (including butnot limited to, in unnatural amino acid p-propargyloxyphenylalanine) andthe second reactive group is the azido moiety. In another example, thefirst reactive group is the azido moiety (including but not limited to,in the unnatural amino acid p-azido-L-phenylalanine) and the secondreactive group is the alkynyl moiety.

A subset of exemplary sites for incorporation of a non-naturally encodedamino acid include, but are not limited to, 1, 2, 4, 17, 21, 24, 27, 28,30, 31, 32, 34, 36, 37, 38, 40, 50, 53, 55, 58, 65, 68, 72, 76, 80, 82,83, 85, 86, 87, 89, 113, 115, 116, 119, 120, 121, 122, 123, 124, 125,126, 127, 128, 129, 130, 131, 132, 134, 136, and 162. An examination ofthe crystal structure of hEPO and its interactions with the hEPOreceptor indicates as well as the molecular modeling provided along withthe presently filed application of fEPO indicate that the side chains ofthese amino acid residues are fully or partially accessible to solventand the side chain of a non-naturally encoded amino acid may point awayfrom the protein surface and out into the solvent.

Exemplary positions for incorporation of a non-naturally encoded aminoacid into fEPO include 21, 24, 28, 30, 31, 36, 37, 38, 55, 72, 83, 85,86, 87, 89, 113, 116, 119, 120, 121, 123, 124, 125, 126, 127, 128, 129,130, and 162. An examination of the crystal structure of hEPO and itsinteractions with the hEPO receptor indicates that the side chains ofthese amino acid residues are fully exposed to the solvent and the sidechain of the native residue points out into the solvent.

In some cases, the non-naturally encoded amino acid substitution(s) orincorporation(s) will be combined with other additions, substitutions,or deletions within the fEPO polypeptide to affect other biologicaltraits of fEPO. In some cases, the other additions, substitutions ordeletions may increase the stability (including but not limited to,resistance to proteolytic degradation) of the fEPO polypeptide orincrease affinity of the fEPO polypeptide for an erythropoietinreceptor. In some cases, the other additions, substitutions or deletionsmay increase the solubility (including but not limited to, whenexpressed in E. coli or other host cells) of the fEPO polypeptide. Insome embodiments sites are selected for substitution with a naturallyencoded or non-naturally encoded amino acid in addition to another sitefor incorporation of a non-naturally encoded amino acid for the purposeof increasing fEPO solubility following expression in E. colirecombinant host cells. Examples of such sites in fEPO for amino acidsubstitution to increase solubility are N36, Q86, G113 and/or Q115,which may be substituted with Lys, Arg, Glu, or any other chargednaturally encoded or non-naturally encoded amino acid. In someembodiments, the fEPO polypeptides comprise another addition,substitution, or deletion that modulates affinity for the fEPO receptor,modulates (including but not limited to, increases or decreases)receptor dimerization, stabilizes receptor dimers, modulates circulatinghalf-life, modulates release or bio-availabilty, facilitatespurification, or improves or alters a particular route ofadministration. Similarly, fEPO polypeptides can comprise proteasecleavage sequences, reactive groups, antibody-binding domains (includingbut not limited to, FLAG or poly-His) or other affinity based sequences(including but not limited to, FLAG, poly-His, GST, etc.) or linkedmolecules (including but not limited to, biotin) that improve detection(including but not limited to, GFP), purification or other traits of thepolypeptide.

For instance, in addition to introducing one or more non-naturallyencoded amino acids as set forth herein, one or more of the followingsubstitutions are introduced: S9A, F48S, Y49S, A50S, Q59A, A73G, G101A,T106A, L108A, T132A, R139A, K140A, R143A, S146A, N147A, R150A, and K154Ato increase the affinity of the fEPO variant for its receptor (Wen etal., (1994) JBC 269:22839-22846).

In some embodiments, the substitution of a non-naturally encoded aminoacid generates a fEPO antagonist. A subset of exemplary sites forincorporation of a non-naturally encoded amino acid include: 10, 11, 14,15, 96, 97, 100, 103, 104, 107, 110. (Elliot et al. (1997) Blood 89:493-502; and Cheetham et al. (1998) Nature Structural Biology 5:861-866). In other embodiments, the exemplary sites of incorporation ofa non-naturally encoded amino acid include residues within the aminoterminal region of helix A and a portion of helix C. In anotherembodiment, substitution of L108 with a non-naturally encoded amino acidsuch as p-azido-L-phenyalanine or O-propargyl-L-tyrosine. In otherembodiments, the above-listed substitutions are combined with additionalsubstitutions that cause the fEPO polypeptide to be a fEPO antagonist.For instance, a non-naturally encoded amino acid is substituted at oneof the positions identified herein and a simultaneous substitution isintroduced at L108 (including but not limited to, L108K, L108R, L108II,L108D, or L108E).

In some cases, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or more amino acids aresubstituted with a non-naturally-encoded amino acid. In some cases, thefEPO polypeptide further includes 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or moresubstitutions of a non-naturally encoded amino acid for anaturally-occurring amino acid. For example, in some embodiments, atleast two residues in the following regions of fEPO are substituted witha non-naturally encoded amino acid: 1-7 (N-terminus), 8-26 (A helix),27-38 (region between A helix and B helix), 39-41 (Beta sheet 1), 42-46(region between Beta sheet 1 and mini helix B′), 47-52 (mini B′ helix),53-54 (region between mini B′ helix and B helix), 55-83 (B helix), 84-89(region between B helix and C helix), 90-113 (C helix), 114-121 (mini C′helix), 122-132 (region between mini C′ helix and Beta sheet 2), 133-135(Beta sheet 2), 136-137 (region between Beta sheet 2 and D helix),138-161 (D helix), 162-166 (C-terminus). In some cases, the two or morenon-naturally encoded residues are linked to one or more lower molecularweight linear or branched PEGs (approximately ˜5-20 kDa in mass),thereby enhancing binding affinity and comparable serum half-liferelative to the species attached to a single, higher molecular weightPEG.

In some embodiments, up to two of the following residues are substitutedwith a non-naturally-encoded amino acid at position: 1, 2, 4, 17, 21,24, 27, 28, 30, 31, 32, 34, 36, 37, 38, 40, 50, 53, 55, 58, 65, 68, 72,76, 80, 82, 83, 85, 86, 87, 89, 113, 115, 116, 119, 120, 121, 122, 123,124, 125, 126, 127, 128, 129, 130, 131, 132, 134, 136, and 162. Thus, insome cases, any of the following pairs of substitutions are made: N24X*and G113X*; N38X* and Q115X*; N36X* and S85X*; N36X* and A125X*; N36X*and A128X*; Q86X* and S126X* wherein X* represents a non-naturallyencoded amino acid. Preferred sites for incorporation of two or morenon-naturally encoded amino acids include combinations of the followingresidues: 21, 24, 28, 30, 31, 36, 37, 38, 55, 72, 83, 85, 86, 87, 89,113, 116, 119, 120, 121, 123, 124, 125, 126, 127, 128, 129, 130, and162. Particularly preferred sites for incorporation of two or morenon-naturally encoded amino acids include combinations of the followingresidues: 21, 24, 38, 83, 86, 89, 116, 119, 124, 125, 126, 127, 128,129, 130 and 162.

VIII. Expression in Non-Eukaryotes and Eukaryotes

To obtain high level expression of a cloned fEPO polynucleotide, onetypically subclones polynucleotides encoding a fEPO polypeptide of theinvention into an expression vector that contains a strong promoter todirect transcription, a transcription/translation terminator, and if fora nucleic acid encoding a protein, a ribosome binding site fortranslational initiation. Suitable bacterial promoters are well known inthe art and described, e.g., in Sambrook et al. and Ausubel et al.

Bacterial expression systems for expressing fEPO polypeptides of theinvention are available in, including but not limited to, E. coli,Bacillus sp., and Salmonella (Palva et al., Gene 22:229-235 (1983);Mosbach et al., Nature 302:543-545 (1983). Kits for such expressionsystems are commercially available. Eukaryotic expression systems formammalian cells, yeast, and insect cells are well known in the art andare also commercially available. In cases where orthogonal tRNAs andamino acyl tRNA synthetases (described above) are used to express thefEPO polypeptides of the invention, host cells for expression areselected based on their ability to use the orthogonal components.Exemplary host cells include Gram-positive bacteria (including but notlimited to B. brevis or B. subtilis, Pseudomonas or Streptomyces) andGram-negative bacteria (E. coli), as well as yeast and other eukaryoticcells. Cells comprising O-tRNA/O-RS pairs can be used as describedherein.

A eukaryotic host cell or non-eukaryotic host cell of the presentinvention provides the ability to synthesize proteins that compriseunnatural amino acids in large useful quantities. In one aspect, thecomposition optionally includes, including but not limited to, at least10 micrograms, at least 50 micrograms, at least 75 micrograms, at least100 micrograms, at least 200 micrograms, at least 250 micrograms, atleast 500 micrograms, at least 1 milligram, at least 10 milligrams, atleast 100 milligrams, at least one gram, or more of the protein thatcomprises an unnatural amino acid, or an amount that can be achievedwith in vivo protein production methods (details on recombinant proteinproduction and purification are provided herein). In another aspect, theprotein is optionally present in the composition at a concentration of,including but not limited to, at least 10 micrograms of protein perliter, at least 50 micrograms of protein per liter, at least 75micrograms of protein per liter, at least 100 micrograms of protein perliter, at least 200 micrograms of protein per liter, at least 250micrograms of protein per liter, at least 500 micrograms of protein perliter, at least 1 milligram of protein per liter, or at least 10milligrams of protein per liter or more, in, including but not limitedto, a cell lysate, a buffer, a pharmaceutical buffer, or other liquidsuspension (including but not limited to, in a volume of, including butnot limited to, anywhere from about 1 nl to about 100 L). The productionof large quantities (including but not limited to, greater that thattypically possible with other methods, including but not limited to, invitro translation) of a protein in a eukaryotic cell including at leastone unnatural amino acid is a feature of the invention.

A eukaryotic host cell or non-eukaryotic hose cell of the presentinvention provides the ability to biosynthesize proteins that compriseunnatural amino acids in large useful quantities. For example, proteinscomprising an unnatural amino acid can be produced at a concentrationof, including but not limited to, at least 10 μg/liter, at least 50μg/liter, at least 75 μg/liter, at least 100 μg/liter, at least 200μg/liter, at least 250 μg/liter, or at least 500 μg/liter, at least 1mg/liter, at least 2 mg/liter, at least 3 mg/liter, at least 4 mg/liter,at least 5 mg/liter, at least 6 mg/liter, at least 7 mg/liter, at least8 mg/liter, at least 9 mg/liter, at least 10 mg/liter, at least 20, 30,40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 600, 700, 800, 900mg/liter, 1 g/liter, 5 g/liter, 10 g/liter or more of protein in a cellextract, cell lysate, culture medium, a buffer, and/or the like.

Expression Systems, Culture, and Isolation

fEPO may be expressed in any number of suitable expression systemsincluding, for example, yeast, insect cells, mammalian cells, andbacteria. A description of exemplary expression systems is providedbelow.

Yeast As used herein, the term “yeast” includes any of the variousyeasts capable of expressing a gene encoding fEPO. Such yeasts include,but are not limited to, ascosporogenous yeasts (Endomycetales),basidiosporogenous yeasts and yeasts belonging to the Fungi imperfecti(Blastomycetes) group. The ascosporogenous yeasts are divided into twofamilies, Spermophthoraceae and Saccharomycetaceae. The latter iscomprised of four subfamilies, Schizosaccharomycoideae (e.g., genusSchizosaccharomyces), Nadsonioideae, Lipomycoideae and Saccharomycoideae(e.g., genera Pichia, Kluyveromyces and Saccharomyces). Thebasidiosporogenous yeasts include the genera Leucosporidium,Rhodosporidium, Sporidiobolus, Filobasidium, and Filobasidiella. Yeastsbelonging to the Fungi Imperfecti (Blastomycetes) group are divided intotwo families, Sporobolomycetaceae (e.g., genera Sporobolomyces andBullera) and Cryptococcaceae (e.g., genus Candida).

Of particular interest for use with the present invention are specieswithin the genera Pichia, Kluyveromyces, Saccharomyces,Schizosaccharomyces, Hansenula, Torulopsis, and Candida, including, butnot limited to, P. pastoris, P. guillerimondii, S. cerevisiae, S.carlsbergensis, S. diastaticus, S. douglasii, S. kluyveri, S, norbensis,S. oviformis, K. lactis, K. fragilis, C. albicans, C. maltoses, and H.polymorpha.

The selection of suitable yeast for expression of fEPO is within theskill of one of ordinary skill in the art. In selecting yeast hosts forexpression, suitable hosts may include those shown to have, for example,good secretion capacity, low proteolytic activity, and overallrobustness. Yeast are generally available from a variety of sourcesincluding, but not limited to, the Yeast Genetic Stock Center,Department of Biophysics and Medical Physics, University of California(Berkeley, Calif.), and the American Type Culture Collection (“ATCC”)(Manassas, Va.).

The term “yeast host” or “yeast host cell” includes yeast that can be,or has been, used as a recipient for recombinant vectors or othertransfer DNA. The term includes the progeny of the original yeast hostcell that has received the recombinant vectors or other transfer DNA. Itis understood that the progeny of a single parental cell may notnecessarily be completely identical in morphology or in genomic or totalDNA complement to the original parent, due to accidental or deliberatemutation. Progeny of the parental cell that are sufficiently similar tothe parent to be characterized by the relevant property, such as thepresence of a nucleotide sequence encoding a fEPO, are included in theprogeny intended by this definition.

Expression and transformation vectors, including extrachromosomalreplicons or integrating vectors, have been developed for transformationinto many yeast hosts. For example, expression vectors have beendeveloped for S. cerevisiae (Sikorski et al., GENETICS (1998) 112:19;Ito et al., J. BACTERIOL. (1983) 153:163; Hinnen et al., PROC. NATL.ACAD. SCI. USA (1978) 75:1929); C. albicans (Kurtz et al., MOL. CELL.BIOL. (1986) 6:142); C. maltosa (Kunze et al., J. BASIC MICROBIOL.(1985) 25:141); H. polymorpha (Gleeson et al., J. GEN. MICROBIOL. (1986)132:3459; Roggenkamp et al., MOL. GEN. GENET. (1986) 202:302); K.fragilis (Das et al., J. BACTERIOL. (1984) 158:1165); K. lactis (DeLouvencourt et al., J. BACTERIOL. (1983) 154:737; Van den Berg et al.,BIO/TECHNOLOGY (1990) 8:135); P. guillerimondii (Kunze et al., J. BASICMICROBIOL. (1985) 25:141); P. pastoris (U.S. Pat. Nos. 5,324,639;4,929,555; and 4,837,148; Cregg et al., MOL. CELL. BIOL. (1985) 5:3376);Schizosaccharomyces pombe (Beach and Nurse, NATURE (1981) 300:706); andY. lipolytica (Davidow et al., CURR. GENET. (1985) 10:380 (1985);Gaillardin et al., CURR. GENET. (1985) 10:49); A. nidulans (Ballance etal., BIOCHEM. BIOPHYS. RES. COMMUN. (1983) 112:284-89; Tilbum et al.,GENE (1983) 26:205-221; and Yelton et al., PROC. NATL. ACAD. SCI. USA(1984) 81:1470-74); A. niger (Kelly and Hynes, EMBO J. (1985) 4:475479);T. reesia (EP 0 244 234); and filamentous fungi such as, e.g.,Neurospora, Penicillium, Tolypocladium (WO 91/00357).

Control sequences for yeast vectors are well known to those of ordinaryskill in the art and include, but are not limited to, promoter regionsfrom genes such as alcohol dehydrogenase (ADH) (EP 0 284 044); enolase;glucokinase; glucose-6-phosphate isomerase;glyceraldehydes-3-phosphate-dehydrogenase (GAP or GAPDH); hexokinase;phosphofructokinase; 3-phosphoglycerate mutase; and pyruvate kinase(PyK) (EP 0 329 203). The yeast PHO5 gene, encoding acid phosphatase,also may provide useful promoter sequences (Myanohara et al., PROC.NATL. ACAD. SCI. USA (1983) 80:1). Other suitable promoter sequences foruse with yeast hosts may include the promoters for 3-phosphoglyceratekinase (Hitzeman et al., J. BIOL. CHEM. (1980) 255:2073); and otherglycolytic enzymes, such as pyruvate decarboxylase, triosephosphateisomerase, and phosphoglucose isomerase (Holland et al., BIOCHEMISTRY(1978) 17:4900; Hess et al., J. ADV. ENZYME REG. (1968) 7:149).Inducible yeast promoters having the additional advantage oftranscription controlled by growth conditions may include the promoterregions for alcohol dehydrogenase 2; isocytochrome C; acid phosphatase;metallothionein; glyceraldehyde-3-phosphate dehydrogenase; degradativeenzymes associated with nitrogen metabolism; and enzymes responsible formaltose and galactose utilization. Suitable vectors and promoters foruse in yeast expression are further described in EP 0 073 657.

Yeast enhancers also may be used with yeast promoters. In addition,synthetic promoters may also function as yeast promoters. For example,the upstream activating sequences (UAS) of a yeast promoter may bejoined with the transcription activation region of another yeastpromoter, creating a synthetic hybrid promoter. Examples of such hybridpromoters include the ADH regulatory sequence linked to the GAPtranscription activation region. See U.S. Pat. Nos. 4,880,734 and4,876,197. Other examples of hybrid promoters include promoters thatconsist of the regulatory sequences of the ADH2, GAL4, GAL10, or PHO5genes, combined with the transcriptional activation region of aglycolytic enzyme gene such as GAP or PyK. See EP 0 164 556.Furthermore, a yeast promoter may include naturally occurring promotersof non-yeast origin that have the ability to bind yeast RNA polymeraseand initiate transcription.

Other control elements that may comprise part of the yeast expressionvectors include terminators, for example, from GAPDH or the enolasegenes (Holland et al., J. BIOL. CHEM. (1981) 256:1385). In addition, theorigin of replication from the 2μ plasmid origin is suitable for yeast.A suitable selection gene for use in yeast is the trp1 gene present inthe yeast plasmid. See Tschemper et al., GENE (1980) 10:157; Kingsman etal., GENE (1979) 7:141. The trp1 gene provides a selection marker for amutant strain of yeast lacking the ability to grow in tryptophan.Similarly, Leu2-deficient yeast strains (ATCC 20,622 or 38,626) arecomplemented by known plasmids bearing the Leu2 gene.

Methods of introducing exogenous DNA into yeast hosts are well known tothose of ordinary skill in the art, and typically include, but are notlimited to, either the transformation of spheroplasts or of intact yeasthost cells treated with alkali cations. For example, transformation ofyeast can be carried out according to the method described in Hsiao etal., PROC. NATL. ACAD. SCI. USA (1979) 76:3829 and Van Solingen et al.,J. BACT. (1977) 130:946. However, other methods for introducing DNA intocells such as by nuclear injection, electroporation, or protoplastfusion may also be used as described generally in SAMBROOK ET AL.,MOLECULAR CLONING: A LAB. MANUAL (2001). Yeast host cells may then becultured using standard techniques known to those of ordinary skill inthe art.

Other methods for expressing heterologous proteins in yeast host cellsare well known to those of ordinary skill in the art. See generally U.S.Patent Application No. 20020055169, U.S. Pat. Nos. 6,361,969; 6,312,923;6,183,985; 6,083,723; 6,017,731; 5,674,706; 5,629,203; 5,602,034; and5,089,398; U.S. Reexamined Patent Nos. RE37,343 and RE35,749; PCTPublished Patent Applications WO 99/078621; WO 98/37208; and WO98/26080; European Patent Applications EP 0 946 736; EP 0 732 403; EP 0480 480; EP 0 460 071; EP 0 340 986; EP 0 329 203; EP 0 324 274; and EP0 164 556. See also Gellissen et al., ANTONIE VAN LEEUWENHOEK (1992)62(1-2):79-93; Romanos et al., YEAST (1992) 8(6):423-488; Goeddel,METHODS IN ENZYMOLOGY (1990) 185:3-7.

The yeast host strains may be grown in fermentors during theamplification stage using standard feed batch fermentation methods wellknown to those of ordinary skill in the art. The fermentation methodsmay be adapted to account for differences in a particular yeast host'scarbon utilization pathway or mode of expression control. For example,fermentation of a Saccharomyces yeast host may require a single glucosefeed, complex nitrogen source (e.g., casein hydrolysates), and multiplevitamin supplementation. In contrast, the methylotrophic yeast P.pastoris may require glycerol, methanol, and trace mineral feeds, butonly simple ammonium (nitrogen) salts for optimal growth and expression.See, e.g., U.S. Pat. No. 5,324,639; Elliott et al., J. PROTEIN CHEM.(1990) 9:95; and Fieschko et al., BIOTECH. BIOENG. (1987) 29:1113.

Such fermentation methods, however, may have certain common featuresindependent of the yeast host strain employed. For example, a growthlimiting nutrient, typically carbon, may be added to the fermentorduring the amplification phase to allow maximal growth. In addition,fermentation methods generally employ a fermentation medium designed tocontain adequate amounts of carbon, nitrogen, basal salts, phosphorus,and other minor nutrients (vitamins, trace minerals and salts, etc.).Examples of fermentation media suitable for use with Pichia aredescribed in U.S. Pat. Nos. 5,324,639 and 5,231,178.

Baculovirus-Infected Insect Cells The term “insect host” or “insect hostcell” refers to a insect that can be, or has been, used as a recipientfor recombinant vectors or other transfer DNA. The term includes theprogeny of the original insect host cell that has been transfected. Itis understood that the progeny of a single parental cell may notnecessarily be completely identical in morphology or in genomic or totalDNA complement to the original parent, due to accidental or deliberatemutation. Progeny of the parental cell that are sufficiently similar tothe parent to be characterized by the relevant property, such as thepresence of a nucleotide sequence encoding a fEPO polypeptide, areincluded in the progeny intended by this definition.

The selection of suitable insect cells for expression of fEPO is wellknown to those of ordinary skill in the art. Several insect species arewell described in the art and are commercially available including Aedesaegypti, Bombyx mori, Drosophila melanogaster, Spodoptera frugiperda,and Trichoplusia ni. In selecting insect hosts for expression, suitablehosts may include those shown to have, inter alfa, good secretioncapacity, low proteolytic activity, and overall robustness. Insect aregenerally available from a variety of sources including, but not limitedto, the Insect Genetic Stock Center, Department of Biophysics andMedical Physics, University of California (Berkeley, Calif.); and theAmerican Type Culture Collection (“ATCC”) (Manassas, Va.).

Generally, the components of a baculovirus-infected insect expressionsystem include a transfer vector, usually a bacterial plasmid, whichcontains both a fragment of the baculovirus genome, and a convenientrestriction site for insertion of the heterologous gene to be expressed;a wild type baculovirus with a sequences homologous to thebaculovirus-specific fragment in the transfer vector (this allows forthe homologous recombination of the heterologous gene in to thebaculovirus genome); and appropriate insect host cells and growth media.The materials, methods and techniques used in constructing vectors,transfecting cells, picking plaques, growing cells in culture, and thelike are known in the art and manuals are available describing thesetechniques.

After inserting the heterologous gene into the transfer vector, thevector and the wild type viral genome are transfected into an insecthost cell where the vector and viral genome recombine. The packagedrecombinant virus is expressed and recombinant plaques are identifiedand purified. Materials and methods for baculovirus/insect cellexpression systems are commercially available in kit form from, forexample, Invitrogen Corp. (Carlsbad, Calif.). These techniques aregenerally known to those skilled in the art and fully described inSUMMERS AND SMITH, TEXAS AGRICULTURAL EXPERIMENT STATION BULLETIN NO.1555 (1987), herein incorporated by reference. See also, RICHARDSON, 39METHODS IN MOLECULAR BIOLOGY: BACULOVIRUS EXPRESSION PROTOCOLS (1995);AUSUBEL ET AL., CURRENT PROTOCOLS IN MOLECULAR BIOLOGY 16.9-16.11(1994); KING AND POSSEE, THE BACULOVIRUS SYSTEM: A LABORATORY GUIDE(1992); and O'REILLY ET AL., BACULOVIRUS EXPRESSION VECTORS: ALABORATORY MANUAL (1992).

Indeed, the production of various heterologous proteins usingbaculovirus/insect cell expression systems is well known in the art.See, e.g., U.S. Pat. Nos. 6,368,825; 6,342,216; 6,338,846; 6,261,805;6,245,528, 6,225,060; 6,183,987; 6,168,932; 6,126,944; 6,096,304;6,013,433; 5,965,393; 5,939,285; 5,891,676; 5,871,986; 5,861,279;5,858,368; 5,843,733; 5,762,939; 5,753,220; 5,605,827; 5,583,023;5,571,709; 5,516,657; 5,290,686; WO 02/06305; WO 01/90390; WO 01/27301;WO 01/05956; WO 00/55345; WO 00/20032 WO 99/51721; WO 99/45130; WO99/31257; WO 99/10515; WO 99/09193; WO 97/26332; WO 96/29400; WO96/25496; WO 96/06161; WO 95/20672; WO 93/03173; WO 92/16619; WO92/03628; WO 92/01801; WO 90/14428; WO 90/10078; WO 90/02566; WO90/02186; WO 90/01556; WO 89/01038; WO 89/01037; WO 88/07082.

Vectors that are useful in baculovirus/insect cell expression systemsare known in the art and include, for example, insect expression andtransfer vectors derived from the baculovirus Autographacalifornicanuclear polyhedrosis virus (AcNPV), which is a helper-independent, viralexpression vector. Viral expression vectors derived from this systemusually use the strong viral polyhedrin gene promoter to driveexpression of heterologous genes. See generally, Reilly ET AL.,BACULOVIRUS EXPRESSION VECTORS: A LABORATORY MANUAL (1992).

Prior to inserting the foreign gene into the baculovirus genome, theabove-described components, comprising a promoter, leader (if desired),coding sequence of interest, and transcription termination sequence, aretypically assembled into an intermediate transplacement construct(transfer vector). Intermediate transplacement constructs are oftenmaintained in a replicon, such as an extra chromosomal element (e.g.,plasmids) capable of stable maintenance in a host, such as bacteria. Thereplicon will have a replication system, thus allowing it to bemaintained in a suitable host for cloning and amplification. Morespecifically, the plasmid may contain the polyhedrin polyadenylationsignal (Miller et al., ANN. REV. MICROBIOL. (1988) 42:177) and aprokaryotic ampicillin-resistance (amp) gene and origin of replicationfor selection and propagation in E. coli.

One commonly used transfer vector for introducing foreign genes intoAcNPV is pAc373. Many other vectors, known to those of skill in the art,have also been designed including, for example, pVL985, which alters thepolyhedrin start codon from ATG to ATT, and which introduces a BamHIcloning site 32 base pairs downstream from the ATT. See Luckow andSummers, 17 VIROLOGY 31 (1989). Other commercially available vectorsinclude, for example, PBlueBac4.5/V5-His; pBlueBacHis2; pMelBac;pBlueBac4.5 (Invitrogen Corp., Carlsbad, Calif.).

After insertion of the heterologous gene, the transfer vector and wildtype baculoviral genome are co-transfected into an insect cell host.Methods for introducing heterologous DNA into the desired site in thebaculovirus virus are known in the art. See SUMMERS AND SMITH, TEXASAGRICULTURAL EXPERIMENT STATION BULLETIN NO. 1555 (1987); Smith et al.,MOL. CELL. BIOL. (1983) 3:2156; Luckow and Summers, VIROLOGY (1989)17:31. For example, the insertion can be into a gene such as thepolyhedrin gene, by homologous double crossover recombination; insertioncan also be into a restriction enzyme site engineered into the desiredbaculovirus gene. See Miller et al., BIOESSAYS (1989) 4:91.

Transfection may be accomplished by electroporation. See TROTTER ANDWOOD, 39 METHODS IN MOLECULAR BIOLOGY (1995); Mann and King, J. GEN.VIROL. (1989) 70:3501. Alternatively, liposomes may be used to transfectthe insect cells with the recombinant expression vector and thebaculovirus. See, e.g., Liebman et al., BIOTECHNIQUES (1999) 26(1):36;Graves et al., BIOCHEMISTRY (1998) 37:6050; Nomura et al., J. BIOL.CHEM. (1998) 273(22):13570; Schmidt et al., PROTEIN EXPRESSION ANDPURIFICATION (1998) 12:323; Siffert et al., NATURE GENETICS (1998)18:45; TILKINS ET AL., CELL BIOLOGY: A LABORATORY HANDBOOK 145-154(1998); Cai et al., PROTEIN EXPRESSION AND PURIFICATION (1997) 10:263;Dolphin et al., NATURE GENETICS (1997) 17:491; Kost et al., GENE (1997)190:139; Jakobsson et al., J. BIOL. CHEM. (1996) 271:22203; Rowles etal., J. BIOL. CHEM. (1996) 271(37):22376; Reversey et al., J. BIOL.CHEM. (1996) 271(39):23607-10; Stanley et al., J. BIOL. CHEM. (1995)270:4121; Sisk et al., J. VIROL. (1994) 68(2):766; and Peng et al.,BIOTECHNIQUES (1993) 14.2:274. Commercially available liposomes include,for example, Cellfectin® and Lipofectin® (Invitrogen, Corp., Carlsbad,Calif.). In addition, calcium phosphate transfection may be used. SeeTROTTER AND WOOD, 39 METHODS IN MOLECULAR BIOLOGY (1995); Kitts, NAR(1990) 18(19):5667; and Mann and King, J. GEN. VIROL. (1989) 70:3501.

Baculovirus expression vectors usually contain a baculovirus promoter. Abaculovirus promoter is any DNA sequence capable of binding abaculovirus RNA polymerase and initiating the downstream (3′)transcription of a coding sequence (e.g., structural gene) into mRNA. Apromoter will have a transcription initiation region which is usuallyplaced proximal to the 5′ end of the coding sequence. This transcriptioninitiation region typically includes an RNA polymerase binding site anda transcription initiation site. A baculovirus promoter may also have asecond domain called an enhancer, which, if present, is usually distalto the structural gene. Moreover, expression may be either regulated orconstitutive.

Structural genes, abundantly transcribed at late times in the infectioncycle, provide particularly useful promoter sequences. Examples includesequences derived from the gene encoding the viral polyhedron protein(FRIESEN ET AL., The Regulation of Baculovirus Gene Expression in THEMOLECULAR BIOLOGY OF BACULOVIRUSES (1986); EP 0 127 839 and 0 155 476)and the gene encoding the p10 protein (Vlak et al., J. GEN. VIROL.(1988) 69:765.

The newly formed baculovirus expression vector is packaged into aninfectious recombinant baculovirus and subsequently grown plaques may bepurified by techniques known to those skilled in the art. See Miller etal., BIOESSAYS (1989) 4:91; SUMMERS AND SMITH, TEXAS AGRICULTURALEXPERIMENT STATION BULLETIN NO. 1555 (1987).

Recombinant baculovirus expression vectors have been developed forinfection into several insect cells. For example, recombinantbaculoviruses have been developed for, inter alia, Aedes aegypti (ATCCNo. CCL-125), Bombyx mori (ATCC No. CRL-8910), Drosophila melanogaster(ATCC No. 1963), Spodoptera frugiperda, and Trichoplusia ni. See W089/046,699; Wright, NATURE (1986) 321:718; Carbonell et al., J. VIROL.(1985) 56:153; Smith et al., MOL. CELL. BIOL. (1983) 3:2156. Seegenerally, Fraser et al., IN VITRO CELL. DEV. BIOL. (1989) 25:225. Morespecifically, the cell lines used for baculovirus expression vectorsystems commonly include, but are not limited to, Sf9 (Spodopterafrugiperda) (ATCC No. CRL-1711), Sf21 (Spodoptera frugiperda)(Invitrogen Corp., Cat. No. 11497-013 (Carlsbad, Calif.)), Tri-368(Trichopulsia ni), and High-Five™ BTI-TN-5B1-4 (Trichopulsia ni).

Cells and culture media are commercially available for both direct andfusion expression of heterologous polypeptides in abaculovirus/expression, and cell culture technology is generally knownto those skilled in the art.

E. Coli Bacterial expression techniques are well known in the art. Awide variety of vectors are available for use in bacterial hosts. Thevectors may be single copy or low or high multicopy vectors. Vectors mayserve for cloning and/or expression. In view of the ample literatureconcerning vectors, commercial availability of many vectors, and evenmanuals describing vectors and their restriction maps andcharacteristics, no extensive discussion is required here. As iswell-known, the vectors normally involve markers allowing for selection,which markers may provide for cytotoxic agent resistance, prototrophy orimmunity. Frequently, a plurality of markers are present, which providefor different characteristics.

A bacterial promoter is any DNA sequence capable of binding bacterialRNA polymerase and initiating the downstream (3″) transcription of acoding sequence (e.g. structural gene) into mRNA. A promoter will have atranscription initiation region which is usually placed proximal to the5′ end of the coding sequence. This transcription initiation regiontypically includes an RNA polymerase binding site and a transcriptioninitiation site. A bacterial promoter may also have a second domaincalled an operator, that may overlap an adjacent RNA polymerase bindingsite at which RNA synthesis begins. The operator permits negativeregulated (inducible) transcription, as a gene repressor protein maybind the operator and thereby inhibit transcription of a specific gene.Constitutive expression may occur in the absence of negative regulatoryelements, such as the operator. In addition, positive regulation may beachieved by a gene activator protein binding sequence, which, if presentis usually proximal (5′) to the RNA polymerase binding sequence. Anexample of a gene activator protein is the catabolite activator protein(CAP), which helps initiate transcription of the lac operon inEscherichia coli (E. coli) [Raibaud et al., ANNU. REV. GENET. (1984)18:173]. Regulated expression may therefore be either positive ornegative, thereby either enhancing or reducing transcription.

Sequences encoding metabolic pathway enzymes provide particularly usefulpromoter sequences. Examples include promoter sequences derived fromsugar metabolizing enzymes, such as galactose, lactose (lac) [Chang etal., NATURE (1977) 198:1056], and maltose. Additional examples includepromoter sequences derived from biosynthetic enzymes such as tryptophan(trp) [Goeddel et al., NUC. ACIDS RES. (1980) 8:4057; Yelverton et al.,NUCL. ACIDS RES. (1981) 9:731; U.S. Pat. No. 4,738,921; EPO Pub. Nos.036 776 and 121 775]. The β-galactosidase (bla) promoter system[Weissmann (1981) “The cloning of interferon and other mistakes.” InInterferon 3 (Ed. I. Gresser)], bacteriophage lambda PL [Shimatake etal., NATURE (1981) 292:128 and T5 [U.S. Pat. No. 4,689,406] promotersystems also provide useful promoter sequences. Preferred methods of thepresent invention utilize strong promoters, such as the T7 promoter toinduce fEPO at high levels. Examples of such vectors are well known inthe art and include the pET29 series from Novagen, and the pPOP vectorsdescribed in WO99/05297. Such expression systems produce high levels offEPO in the host without compromising host cell viability or growthparameters.

In addition, synthetic promoters which do not occur in nature alsofunction as bacterial promoters. For example, transcription activationsequences of one bacterial or bacteriophage promoter may be joined withthe operon sequences of another bacterial or bacteriophage promoter,creating a synthetic hybrid promoter [U.S. Pat. No. 4,551,433]. Forexample, the tac promoter is a hybrid trp-lac promoter comprised of bothtrp promoter and lac operon sequences that is regulated by the lacrepressor [Amann et al., GENE (1983) 25:167; de Boer et al., PROC. NATL.ACAD. SCI. (1983) 80:21]. Furthermore, a bacterial promoter can includenaturally occurring promoters of non-bacterial origin that have theability to bind bacterial RNA polymerase and initiate transcription. Anaturally occurring promoter of non-bacterial origin can also be coupledwith a compatible RNA polymerase to produce high levels of expression ofsome genes in prokaryotes. The bacteriophase T7 RNA polymerase/promotersystem is an example of a coupled promoter system [Studier et al., J.MOL. BIOL. (1986) 189:113; Tabor et al., Proc Natl. Acad. Sci. (1985)82:1074]. In addition, a hybrid promoter can also be comprised of abacteriophage promoter and an E. coli operator region (EPO Pub. No. 267851).

In addition to a functioning promoter sequence, an efficient ribosomebinding site is also useful for the expression of foreign genes inprokaryotes. In E. coli, the ribosome binding site is called theShine-Dalgarno (SD) sequence and includes an initiation codon (ATG) anda sequence 3-9 nucleotides in length located 3-11 nucleotides upstreamof the initiation codon [Shine et al., NATURE (1975) 254:34]. The SDsequence is thought to promote binding of mRNA to the ribosome by thepairing of bases between the SD sequence and the 3′ and of E. coli 16SrRNA [Steitz et al. “Genetic signals and nucleotide sequences inmessenger RNA”, In Biological Regulation and Development: GeneExpression (Ed. R. F. Goldberger, 1979)]. To express eukaryotic genesand prokaryotic genes with weak ribosome-binding site [Sambrook et al.“Expression of cloned genes in Escherichia coli”, Molecular Cloning: ALaboratory Manual, 1989].

The term “bacterial host” or “bacterial host cell” refers to a bacterialthat can be, or has been, used as a recipient for recombinant vectors orother transfer DNA. The term includes the progeny of the originalbacterial host cell that has been transfected. It is understood that theprogeny of a single parental cell may not necessarily be completelyidentical in morphology or in genomic or total DNA complement to theoriginal parent, due to accidental or deliberate mutation. Progeny ofthe parental cell that are sufficiently similar to the parent to becharacterized by the relevant property, such as the presence of anucleotide sequence encoding a fEPO, are included in the progenyintended by this definition.

The selection of suitable host bacteria for expression of fEPO is wellknown to those of ordinary skill in the art. In selecting bacterialhosts for expression, suitable hosts may include those shown to have,inter alfa, good inclusion body formation capacity, low proteolyticactivity, and overall robustness. Bacterial hosts are generallyavailable from a variety of sources including, but not limited to, theBacterial Genetic Stock Center, Department of Biophysics and MedicalPhysics, University of California (Berkeley, Calif.); and the AmericanType Culture Collection (“ATCC”) (Manassas, Va.).Industrial/pharmaceutical fermentation generally use bacterial derivedfrom K strains (e.g. W3110) or from bacteria derived from B strains(e.g. BL21). These strains are particularly useful because their growthparameters are extremely well known and robust. In addition, thesestrains are non-pathogenic, which is commercially important for safetyand environmental reasons. In one embodiment of the methods of thepresent invention, the E. coli host is a strain of BL21. In anotherembodiment of the methods of the present invention, the E. coli host isa protease minus strain including, but not limited to, OMP- and LON-.

Once a recombinant host cell strain has been established (i.e., theexpression construct has been introduced into the host cell and hostcells with the proper expression construct are isolated), therecombinant host cell strain is cultured under conditions appropriatefor production of fEPO. As will be apparent to one of skill in the art,the method of culture of the recombinant host cell strain will bedependent on the nature of the expression construct utilized and theidentity of the host cell. Recombinant host strains are normallycultured using methods that are well known to the art. Recombinant hostcells are typically cultured in liquid medium containing assimilatablesources of carbon, nitrogen, and inorganic salts and, optionally,containing vitamins, amino acids, growth factors, and otherproteinaceous culture supplements well known to the art. Liquid mediafor culture of host cells may optionally contain antibiotics oranti-fungals to prevent the growth of undesirable microorganisms and/orcompounds including, but not limited to, antibiotics to select for hostcells containing the expression vector.

Recombinant host cells may be cultured in batch or continuous formats,with either cell harvesting (in the case where fEPO accumulatesintracellularly) or harvesting of culture supernatant in either batch orcontinuous formats. For production in prokaryotic host cells, batchculture and cell harvest are preferred.

The fEPO of the invention are normally purified after expression inrecombinant systems. fEPO may be purified from host cells by a varietyof methods known to the art. Normally, fEPO produced in bacterial hostcells is poorly soluble or insoluble (in the form of inclusion bodies).In one embodiment of the present invention, amino acid substitutions mayreadily be made in the fEPO polypeptide that are selected for thepurpose of increasing the solubility of the recombinantly producedprotein utilizing the methods disclosed herein as well as those known inthe art. In the case of insoluble protein, the protein may be collectedfrom host cell lysates by centrifugation and may further be followed byhomogenization of the cells. In the case of poorly soluble protein,compounds including, but not limited to, polyethylene imine (PEI) may beadded to induce the precipitation of partially soluble protein. Theprecipitated protein may then be conveniently collected bycentrifugation. Recombinant host cells may be disrupted or homogenizedto release the inclusion bodies from within the cells using a variety ofmethods well known to those of ordinary skill in the art. Host celldisruption or homogenization may be performed using well knowntechniques including, but not limited to, enzymatic cell disruption,sonication, dounce homogenization, or high pressure release disruption.In one embodiment of the method of the present invention, the highpressure release technique is used to disrupt the E. coli host cells torelease the inclusion bodies of fEPO. It has been found that yields ofinsoluble fEPO in the form of inclusion bodies may be increased byutilizing only one passage of the E. coli host cells through thehomogenizer. When handling inclusion bodies of fEPO, it is advantageousto minimize the homogenization time on repetitions in order to maximizethe yield of inclusion bodies without loss due to factors such assolubilization, mechanical shearing or proteolysis.

Insoluble or precipitated fEPO may then be solubilized using any of anumber of suitable solubilization agents known to the art. Preferably,fEPO is solubilized with urea or guanidine hydrochloride. The volume ofthe solubilized fEPO-BP should be minimized so that large batches may beproduced using conveniently manageable batch sizes. This factor may besignificant in a large-scale commercial setting where the recombinanthost may be grown in batches that are thousands of liters in volume. Inaddition, when manufacturing fEPO in a large-scale commercial setting,in particular for human pharmaceutical uses, the avoidance of harshchemicals that can damage the machinery and container, or the proteinproduct itself, should be avoided, if possible. It has been shown in themethod of the present invention that the milder denaturing agent ureacan be used to solubilize the fEPO inclusion bodies in place of theharsher denaturing agent guanidine hydrochloride. The use of ureasignificantly reduces the risk of damage to stainless steel equipmentutilized in the manufacturing and purification process of fEPO whileefficiently solubilizing the fEPO inclusion bodies.

When fEPO is produced as a fusion protein, the fusion sequence ispreferably removed. Removal of a fusion sequence may be accomplished byenzymatic or chemical cleavage, preferably by enzymatic cleavage.Enzymatic removal of fusion sequences may be accomplished using methodswell known to those in the art. The choice of enzyme for removal of thefusion sequence will be determined by the identity of the fusion, andthe reaction conditions will be specified by the choice of enzyme aswill be apparent to one skilled in the art. The cleaved fEPO ispreferably purified from the cleaved fusion sequence by well knownmethods. Such methods will be determined by the identity and propertiesof the fusion sequence and the fEPO, as will be apparent to one skilledin the art. Methods for purification may include, but are not limitedto, size-exclusion chromatography, hydrophobic interactionchromatography, ion-exchange chromatography or dialysis or anycombination thereof.

fEPO is also preferably purified to remove DNA from the proteinsolution. DNA may be removed by any suitable method known to the art,such as precipitation or ion exchange chromatography, but is preferablyremoved by precipitation with a nucleic acid precipitating agent, suchas, but not limited to, protamine sulfate. fEPO may be separated fromthe precipitated DNA using standard well known methods including, butnot limited to, centrifugation or filtration. Removal of host nucleicacid molecules is an important factor in a setting where the fEPO is tobe used to treat humans and the methods of the present invention reducehost cell DNA to pharmaceutically acceptable levels.

Methods for small-scale or large-scale fermentation can also be used inprotein expression, including but not limited to, fermentors, shakeflasks, fluidized bed bioreactors, hollow fiber bioreactors, rollerbottle culture systems, and stirred tank bioreactor systems. Each ofthese methods can be performed in a batch, fed-batch, or continuous modeprocess.

Feline EPO polypeptides of the invention can generally be recoveredusing methods standard in the art. For example, culture medium or celllysate can be centrifuged or filtered to remove cellular debris. Thesupernatant may be concentrated or diluted to a desired volume ordiafiltered into a suitable buffer to condition the preparation forfurther purification. Further purification of the fEPO of the presentinvention include separating deamidated and clipped forms of the fEPOvariant from the intact form.

Any of the following exemplary procedures can be employed forpurification of a fEPO polypeptides of the invention: affinitychromatography; anion- or cation-exchange chromatography (using,including but not limited to, DEAE SEPHAROSE); chromatography on silica;reverse phase HPLC; gel filtration (using, including but not limited to,SEPHADEX G-75); hydrophobic interaction chromatography; size-exclusionchromatography, metal-chelate chromatography;ultrafiltration/diafiltration; ethanol precipitation; ammonium sulfateprecipitation; chromatofocusing; displacement chromatography;electrophoretic procedures (including but not limited to preparativeisoelectric focusing), differential solubility (including but notlimited to ammonium sulfate precipitation), SDS-PAGE, or extraction.

Proteins of the present invention, including but not limited to,proteins comprising unnatural amino acids, antibodies to proteinscomprising unnatural amino acids, binding partners for proteinscomprising unnatural amino acids, etc., can be purified, eitherpartially or substantially to homogeneity, according to standardprocedures known to and used by those of skill in the art. Accordingly,polypeptides of the invention can be recovered and purified by any of anumber of methods well known in the art, including but not limited to,ammonium sulfate or ethanol precipitation, acid or base extraction,column chromatography, affinity column chromatography, anion or cationexchange chromatography, phosphocellulose chromatography, hydrophobicinteraction chromatography, hydroxylapatite chromatography, lectinchromatography, gel electrophoresis and the like. Protein refoldingsteps can be used, as desired, in making correctly folded matureproteins. High performance liquid chromatography (HPLC), affinitychromatography or other suitable methods can be employed in finalpurification steps where high purity is desired. In one embodiment,antibodies made against unnatural amino acids (or proteins comprisingunnatural amino acids) are used as purification reagents, including butnot limited to, for affinity-based purification of proteins comprisingone or more unnatural amino acid(s). Once purified, partially or tohomogeneity, as desired, the polypeptides are optionally used for a widevariety of utilities, including but not limited to, as assay components,therapeutics, prophylaxis, diagnostics, research reagents, and/or asimmunogens for antibody production.

In addition to other references noted herein, a variety ofpurification/protein folding methods are well known in the art,including, but not limited to, those set forth in R. Scopes, ProteinPurification, Springer-Verlag, N.Y. (1982); Deutscher, Methods inEnzymology Vol. 182: Guide to Protein Purification, Academic Press, Inc.N.Y. (1990); Sandana (1997) Bioseparation of Proteins, Academic Press,Inc.; Bollag et al. (1996) Protein Methods, 2nd Edition Wiley-Liss, NY;Walker (1996) The Protein Protocols Handbook Humana Press, NJ, Harrisand Angal (1990) Protein Purification Applications: A Practical ApproachIRL Press at Oxford, Oxford, England; Harris and Angal ProteinPurification Methods: A Practical Approach IRL Press at Oxford, Oxford,England; Scopes (1993) Protein Purification: Principles and Practice 3rdEdition Springer Verlag, NY; Janson and Ryden (1998) ProteinPurification: Principles, High Resolution Methods and Applications,Second Edition Wiley-VCH, NY; and Walker (1998) Protein Protocols onCD-ROM Humana Press, NJ; and the references cited therein.

One advantage of producing a protein or polypeptide of interest with anunnatural amino acid in a eukaryotic host cell or non-eukaryotic hostcell is that typically the proteins or polypeptides will be folded intheir native conformations. However, in certain embodiments of theinvention, those of skill in the art will recognize that, aftersynthesis, expression and/or purification, proteins can possess aconformation different from the desired conformations of the relevantpolypeptides. In one aspect of the invention, the expressed protein isoptionally denatured and then renatured. This is accomplished utilizingmethods known in the art, including but not limited to, by adding achaperonin to the protein or polypeptide of interest, by solubilizingthe proteins in a chaotropic agent such as guanidine HCl, utilizingprotein disulfide isomerase, etc.

In general, it is occasionally desirable to denature and reduceexpressed polypeptides and then to cause the polypeptides to re-foldinto the preferred conformation. For example, guanidine, urea, DTT, DTE,and/or a chaperonin can be added to a translation product of interest.Methods of reducing, denaturing and renaturing proteins are well knownto those of skill in the art (see, the references above, and Debinski,et al. (1993) J. Biol. Chem., 268: 14065-14070; Kreitman and Pastan(1993) Bioconjug. Chem., 4: 581-585; and Buchner, et al., (1992) Anal.Biochem., 205: 263-270). Debinski, et al., for example, describe thedenaturation and reduction of inclusion body proteins in guanidine-DTE.The proteins can be refolded in a redox buffer containing, including butnot limited to, oxidized glutathione and L-arginine. Refolding reagentscan be flowed or otherwise moved into contact with the one or morepolypeptide or other expression product, or vice-versa.

In the case of prokaryotic production of fEPO, the fEPO thus producedmay be misfolded and thus lacks or has reduced biological activity. Thebioactivity of the protein may be restored by “refolding”. In general,misfolded fEPO is refolded by solubilizing (where the fEPO is alsoinsoluble), unfolding and reducing the polypeptide chain using, forexample, one or more chaotropic agents (e.g. urea and/or guanidine) anda reducing agent capable of reducing disulfide bonds (e.g.dithiothreitol, DTT or 2-mercaptoethanol, 2-ME). At a moderateconcentration of chaotrope, an oxidizing agent is then added (e.g.,oxygen, cystine or cystamine), which allows the reformation of disulfidebonds. fEPO may be refolded using standard methods known in the art,such as those described in U.S. Pat. Nos. 4,511,502, 4,511,503, and4,512,922. The fEPO may also be cofolded with other proteins to formheterodimers or heteromultimers. After refolding or cofolding, the fEPOis preferably further purified.

General Purification Methods. Any one of a variety of isolation stepsmay be performed on the cell lysate comprising fEPO or on any fEPOmixtures resulting from any isolation steps including, but not limitedto, affinity chromatography, ion exchange chromatography, hydrophobicinteraction chromatography, gel filtration chromatography, highperformance liquid chromatography (“HPLC”), reversed phase-HPLC(“RP-HPLC”), expanded bed adsorption, or any combination and/orrepetition thereof and in any appropriate order.

Equipment and other necessary materials used in performing thetechniques described herein are commercially available. Pumps, fractioncollectors, monitors, recorders, and entire systems are available from,for example, Applied Biosystems (Foster City, Calif.), Bio-RadLaboratories, Inc. (Hercules, Calif.), and Amersham Biosciences, Inc.(Piscataway, N.J.). Chromatographic materials including, but not limitedto, exchange matrix materials, media, and buffers are also availablefrom such companies.

Equilibration, and other steps in the column chromatography processesdescribed herein such as washing and elution, may be more rapidlyaccomplished using specialized equipment such as a pump. Commerciallyavailable pumps include, but are not limited to, HILOAD® Pump P-50,Peristaltic Pump P-1, Pump P-901, and Pump P-903 (Amersham Biosciences,Piscataway, N.J.).

Examples of fraction collectors include RediFrac Fraction Collector,FRAC-100 and FRAC-200 Fraction Collectors, and SUPERFRAC® FractionCollector (Amersham Biosciences, Piscataway, N.J.). Mixers are alsoavailable to form pH and linear concentration gradients. Commerciallyavailable mixers include Gradient Mixer GM-1 and In-Line Mixers(Amersham Biosciences, Piscataway, N.J.).

The chromatographic process may be monitored using any commerciallyavailable monitor. Such monitors may be used to gather information likeUV, pH, and conductivity. Examples of detectors include Monitor UV-1,UVICORD® S II, Monitor UV-M II, Monitor UV-900, Monitor UPC-900, MonitorpH/C-900, and Conductivity Monitor (Amersham Biosciences, Piscataway,N.J.). Indeed, entire systems are commercially available including thevarious AKTA® systems from Amersham Biosciences (Piscataway, N.J.).

In one embodiment of the present invention, for example, the fEPO may bereduced and denatured by first denaturing the resultant purified fEPO inurea, followed by dilution into TRIS buffer containing a reducing agent(such as DTT) at a suitable pH. In another embodiment, the fEPO isdenatured in urea in a concentration range of between about 2 M to about9 M, followed by dilution in TRIS buffer at a pH in the range of about5.0 to about 8.0. The refolding mixture of this embodiment may then beincubated. In one embodiment, the refolding mixture is incubated at roomtemperature for four to twenty-four hours. The reduced and denaturedfEPO mixture may then be further isolated or purified.

As stated herein, the pH of the first fEPO mixture may be adjusted priorto performing any subsequent isolation steps. In addition, the firstfEPO mixture or any subsequent mixture thereof may be concentrated usingtechniques known in the art. Moreover, the elution buffer comprising thefirst fEPO mixture or any subsequent mixture thereof may be exchangedfor a buffer suitable for the next isolation step using techniques wellknown to those of ordinary skill in the art.

Ion Exchange Chromatography. In one embodiment, and as an optional,additional step, ion exchange chromatography may be performed on thefirst fEPO mixture. See generally ION EXCHANGE CHROMATOGRAPHY:PRINCIPLES AND METHODS (Cat. No. 18-1114-21, Amersham Biosciences(Piscataway, N.J.)). Commercially available ion exchange columns includeHITRAP®, HIPREP®, and HILOAD® Columns (Amersham Biosciences, Piscataway,N.J.). Such columns utilize strong anion exchangers such as Q SEPHAROSE®Fast Flow, Q SEPHAROSE® High Performance, and Q SEPHAROSE® XL; strongcation exchangers such as SP SEPHAROSE® High Performance, SP SEPHAROSE®Fast Flow, and SP SEPHAROSE® XL; weak anion exchangers such as DEAESEPHAROSE® Fast Flow; and weak cation exchangers such as CM SEPHAROSE®Fast Flow (Amersham Biosciences, Piscataway, N.J.). Cation exchangecolumn chromatography may be performed on the fEPO at any stage of thepurification process to isolate substantially purified fEPO. The cationexchange chromatography step may be performed using any suitable cationexchange matrix. Useful cation exchange matrices include, but are notlimited to, fibrous, porous, non-porous, microgranular, beaded, orcross-linked cation exchange matrix materials. Such cation exchangematrix materials include, but are not limited to, cellulose, agarose,dextran, polyacrylate, polyvinyl, polystyrene, silica, polyether, orcomposites of any of the foregoing. Following adsorption of the fEPO tothe cation exchanger matrix, substantially purified fEPO may be elutedby contacting the matrix with a buffer having a sufficiently high pH orionic strength to displace the fEPO from the matrix. Suitable buffersfor use in high pH elution of substantially purified fEPO include, butare not limited to, citrate, phosphate, formate, acetate, HEPES, and MESbuffers ranging in concentration from at least about 5 mM to at leastabout 100 mM.

Reverse-Phase Chromatography. RP-HPLC may be performed to purifyproteins following suitable protocols that are known to those ofordinary skill in the art. See, e.g., Pearson et al., ANAL BIOCHEM.(1982) 124:217-230 (1982); Rivier et al., J. CHROM. (1983) 268:112-119;Kunitani et al., J. CHROM. (1986) 359:391-402. RP-HPLC may be performedon the fEPO to isolate substantially purified fEPO. In this regard,silica derivatized resins with alkyl functionalities with a wide varietyof lengths, including, but not limited to, at least about C₃ to at leastabout C₃₀, at least about C₃ to at least about C₂₀, or at least about C₃to at least about C₁₈, resins may be used. Alternatively, a polymericresin may be used. For example, TosoHaas Amberchrome CG1000sd resin maybe used, which is a styrene polymer resin. Cyano or polymeric resinswith a wide variety of alkyl chain lengths may also be used.Furthermore, the RP-HPLC column may be washed with a solvent such asethanol. A suitable elution buffer containing an ion pairing agent andan organic modifier such as methanol, isopropanol, tetrahydrofuran,acetonitrile or ethanol, may be used to elute the fEPO from the RP-HPLCcolumn. The most commonly used ion pairing agents include, but are notlimited to, acetic acid, formic acid, perchlorie acid, phosphoric acid,trifiuoroacetic acid, heptafluorobutyric acid, triethylamine,tetramethylammonium, tetrabutylammonium, triethylammonium acetate.Elution may be performed using one or more gradients or isocraticconditions, with gradient conditions preferred to reduce the separationtime and to decrease peak width. Another method involves the use of twogradients with different solvent concentration ranges. Examples ofsuitable elution buffers for use herein may include, but are not limitedto, ammonium acetate and acetonitrile solutions.

Hydrophobic Interaction Chromatography Purification Techniques.Hydrophobic interaction chromatography (HIC) may be performed on thefEPO. See generally HYDROPHOBIC INTERACTION CHROMATOGRAPHY HANDBOOK:PRINCIPLES AND METHODS (Cat. No. 18-1020-90, Amersham Biosciences(Piscataway, N.J.) which is incorporated by reference herein. SuitableHIC matrices may include, but are not limited to, alkyl- oraryl-substituted matrices, such as butyl-, hexyl-, octyl- orphenyl-substituted matrices including agarose, cross-linked agarose,sepharose, cellulose, silica, dextran, polystyrene, poly(methacrylate)matrices, and mixed mode resins, including but not limited to, apolyethyleneamine resin or a butyl- or phenyl-substitutedpoly(methacrylate) matrix. Commercially available sources forhydrophobic interaction column chromatography include, but are notlimited to, HITRAP®, HIPREP®, and HILOAD® columns (Amersham Biosciences,Piscataway, N.J.). Briefly, prior to loading, the HIC column may beequilibrated using standard buffers known to those of ordinary skill inthe art, such as an acetic acid/sodium chloride solution or HEPEScontaining ammonium sulfate. After loading the fEPO, the column may thenwashed using standard buffers and conditions to remove unwantedmaterials but retaining the fEPO on the HIC column. fEPO may be elutedwith about 3 to about 10 column volumes of a standard buffer, such as aHEPES buffer containing EDTA and lower ammonium sulfate concentrationthan the equilibrating buffer, or an acetic acid/sodium chloride buffer,among others. A decreasing linear salt gradient using, for example, agradient of potassium phosphate, may also be used to elute the fEPOmolecules. The eluant may then be concentrated, for example, byfiltration such as diafiltration or ultrafiltration. Diafiltration maybe utilized to remove the salt used to elute fEPO.

Other Purification Techniques. Yet another isolation step using, forexample, gel filtration (GEL FILTRATION: PRINCIPLES AND METHODS (Cat.No. 18-1022-18, Amersham Biosciences, Piscataway, N.J.) which isincorporated by reference herein, HPLC, expanded bed adsorption,ultrafiltration, diafiltration, lyophilization, and the like, may beperformed on the first fEPO mixture or any subsequent mixture thereof,to remove any excess salts and to replace the buffer with a suitablebuffer for the next isolation step or even formulation of the final drugproduct. The yield of fEPO, including substantially purified fEPO, maybe monitored at each step described herein using techniques known tothose of ordinary skill in the art. Such techniques may also used toassess the yield of substantially purified fEPO following the lastisolation step. For example, the yield of fEPO may be monitored usingany of several reverse phase high pressure liquid chromatographycolumns, having a variety of alkyl chain lengths such as cyano RP-HPLC,C₁₈RP-HPLC; as well as cation exchange HPLC and gel filtration HPLC.

Purity may be determined using standard techniques, such as SDS-PAGE, orby measuring fEPO using Western blot and ELISA assays. For example,polyclonal antibodies may be generated against proteins isolated from anegative control yeast fermentation and the cation exchange recovery.The antibodies may also be used to probe for the presence ofcontaminating host cell proteins.

Additional purification procedures include those described in U.S. Pat.No. 4,612,367 and includes, but is not limited to, (1) applying amixture comprising a fEPO polypeptide to a reverse phase macroporousacrylate ester copolymer resin support at a pH of from about 7 to about9; and (2) eluting the fEPO polypeptide from said support with anaqueous eluant having a pH of from about 7 to about 9 and containingfrom about 20% to about 80% by volume of an organic diluent selectedfrom the group consisting of acetone, acetonitrile, and a combination ofacetone and acetonitrile.

A typical process for the purification of EPO protein is disclosed in WO96/35718, to Burg published Nov. 14, 1996, and is described below. BlueSepharose (Pharmacia) consists of Sepharose beads to the surface ofwhich the Cibacron blue dye is covalently bound. Since EPO binds morestrongly to Blue Sepharose than most non-proteinaceous contaminants,some proteinaceous impurities and PVA, EPO can be enriched in this step.The elution of the Blue Sepharose column is performed by increasing thesalt concentration as well as the pH. The column is filled with 80-100 1of Blue Sepharose, regenerated with NaOH and equilibrated withequilibration buffer (sodium/calcium chloride and sodium acetate). Theacidified and filtered fermenter supernatant is loaded. After completionof the loading, the column is washed first with a buffer similar to theequilibration buffer containing a higher sodium chloride concentrationand consecutively with a TRIS-base buffer. The product is eluted with aTRIS-base buffer and collected in a single fraction in accordance withthe master elution profile.

Butyl Toyopearl 650 C (Toso Haas) is a polystyrene based matrix to whichaliphatic butyl-residues are covalently coupled. Since EPO binds morestrongly to this gel than most of the impurities and PVA, it has to beeluted with a buffer containing isopropanol. The column is packed with30-401 of Butyl Toyopearl 650 C, regenerated with NaOH, washed with aTRIS-base buffer and equilibrated with a TRIS-base buffer containingisopropanol. The Blue Sepharose eluate is adjusted to the concentrationof isopropanol in the column equilibration buffer and loaded onto thecolumn. Then the column is washed with equilibration buffer withincreased isopropanol concentration. The product is eluted with elutionbuffer (TRIS-base buffer with high isopropanol content) and collected ina single fraction in accordance with the master elution profile.

Hydroxyapatite Ultrogel (Biosepra) consists of hydroxyapatite which isincorporated in an agarose matrix to improve the mechanical properties.EPO has a low affinity to hydroxyapatite and can therefore be eluted atlower phosphate concentrations than protein impurities. The column isfilled with 30-401 of Hydroxyapatite Ultrogel and regenerated with apotassium phosphate/calcium chloride buffer and NaOH followed by aTRIS-base buffer. Then it is equilibrated with a TRIS-base buffercontaining a low amount of isopropanol and sodium chloride. The EPOcontaining eluate of the Butyl Toyopearl chromatography is loaded ontothe column. Subsequently the column is washed with equilibration bufferand a TRIS-base buffer without isopropanol and sodium chloride. Theproduct is eluted with a TRIS-base buffer containing a low concentrationof potassium phosphate and collected in a single fraction in accordancewith the master elution profile.

RP-HPLC material Vydac C4 (Vydac)consists of silica gel particles, thesurfaces of which carry C4-alkyl chains. The separation of EPO from theproteinaceous impurities is based on differences in the strength ofhydrophobic interactions. Elution is performed with an acetonitrilegradient in diluted trifluoroacetic acid. Preparative HPLC is performedusing a stainless steel column (filled with 2.8 to 3.2 liter of Vydac C4silicagel). The Hydroxyapatite Ultrogel eluate is acidified by addingtrifluoro-acetic acid and loaded onto the Vydac C4 column. For washingand elution an acetonitrile gradient in diluted trifluoroacetic acid isused. Fractions are collected and immediately neutralized with phosphatebuffer. The EPO fractions which are within the IPC limits are pooled.

DEAE Sepharose (Pharmacia) material consists of diethylaminoethyl(DEAE)-groups which are covalently bound to the surface of Sepharosebeads. The binding of EPO to the DEAE groups is mediated by ionicinteractions. Acetonitrile and trifluoroacetic acid pass through thecolumn without being retained. After these substances have been washedoff, trace impurities are removed by washing the column with acetatebuffer at a low pH. Then the column is washed with neutral phosphatebuffer and EPO is eluted with a buffer with increased ionic strength.The column is packed with DEAE Sepharose fast flow. The column volume isadjusted to assure an EPO load in the range of 3-10 mg EPO/ml gel. Thecolumn is washed with water and equilibration buffer (sodium/potassiumphosphate). The pooled fractions of the HPLC eluate are loaded and thecolumn is washed with equilibration buffer. Then the column is washedwith washing buffer (sodium acetate buffer) followed by washing withequilibration buffer. Subsequently, EPO is eluted from the column withelution buffer (sodium chloride, sodium/potassium phosphate) andcollected in a single fraction in accordance with the master elutionprofile. The eluate of the DEAE Sepharose column is adjusted to thespecified conductivity. The resulting drug substance is sterile filteredinto Teflon bottles and stored at −70° C.

A wide variety of methods and procedures can be used to assess the yieldand purity of a fEPO protein one or more non-naturally encoded aminoacids, including but not limited to, the Bradford assay, SDS-PAGE,silver stained SDS-PAGE, coomassie stained SDS-PAGE, mass spectrometry(including but not limited to, MALDI-TOF) and other methods forcharacterizing proteins known to one skilled in the art.

IX. Expression in Alternate Systems

Several strategies have been employed to introduce unnatural amino acidsinto proteins in non-recombinant host cells, mutagenized host cells, orin cell-free systems. These systems are also suitable for use in makingthe fEPO polypeptides of the present invention.

Derivatization of amino acids with reactive side-chains such as Lys, Cysand Tyr resulted in the conversion of lysine to N²-acetyl-lysine.Chemical synthesis also provides a straightforward method to incorporateunnatural amino acids. With the recent development of enzymatic ligationand native chemical ligation of peptide fragments, it is possible tomake larger proteins. See, e.g., P. E. Dawson and S. B. H. Kent, Annu.Rev. Biochem., 69:923 (2000). A general in vitro biosynthetic method inwhich a suppressor tRNA chemically acylated with the desired unnaturalamino acid is added to an in vitro extract capable of supporting proteinbiosynthesis, has been used to site-specifically incorporate over 100unnatural amino acids into a variety of proteins of virtually any size.See, e.g., V. W. Cornish, D. Mendel and P. G. Schultz, Angew. Chem. Int.Ed. Engl., 1995, 34:621 (1995); C. J. Noren, S. J. Anthony-Cahill, M. C.Griffith, P. G. Schultz, A general method for site-specificincorporation of unnatural amino acids into proteins, Science 244182-188 (1989); and, J. D. Bain, C. G. Glabe, T. A. Dix, A. R.Chamberlin, E. S. Diala, Biosynthetic site-specific incorporation of anon-natural amino acid into a polypeptide, J. Am. Chem. Soc. 1118013-8014 (1989). A broad range of functional groups has been introducedinto proteins for studies of protein stability, protein folding, enzymemechanism, and signal transduction.

An in vivo method, termed selective pressure incorporation, wasdeveloped to exploit the promiscuity of wild-type synthetases. See,e.g., N. Budisa, C. Minks, S. Alefelder, W. Wenger, F, M. Dong, L.Moroder and R. Huber, FASEB J., 13:41 (1999). An auxotrophic strain, inwhich the relevant metabolic pathway supplying the cell with aparticular natural amino acid is switched off, is grown in minimal mediacontaining limited concentrations of the natural amino acid, whiletranscription of the target gene is repressed. At the onset of astationary growth phase, the natural amino acid is depleted and replacedwith the unnatural amino acid analog. Induction of expression of therecombinant protein results in the accumulation of a protein containingthe unnatural analog. For example, using this strategy, o, m andp-fluorophenylalanines have been incorporated into proteins, and exhibittwo characteristic shoulders in the UV spectrum which can be easilyidentified, see, e.g., C. Minks, R. Huber, L. Moroder and N. Budisa,Anal. Biochem., 284:29 (2000); trifluoromethionine has been used toreplace methionine in bacteriophage T4 lysozyme to study its interactionwith chitooligosaccharide ligands by ¹⁹F NMR, see, e.g., H. Duewel, E.Daub, V. Robinson and J. F. Honek, Biochemistry, 36:3404 (1997); andtrifluoroleueine has been incorporated in place of leucine, resulting inincreased thermal and chemical stability of a leucine-zipper protein.See, e.g., Y. Tang, G. Ghirlanda, W. A. Petka, T. Nakajima, W. F.DeGrado and D. A. Tirrell, Angew. Chem. Int. Ed. Engl., 40:1494 (2001).Moreover, selenomethionine and telluromethionine are incorporated intovarious recombinant proteins to facilitate the solution of phases inX-ray crystallography. See, e.g., W. A. Hendrickson, J. R. Horton and D.M. Lemaster, EMBO J., 9:1665 (1990); J. O. Boles, K. Lewinski, M.Kunkle, J. D. Odom, B. Dunlap, L. Lebioda and M. Hatada, Nat. Struct.Biol., 1:283 (1994); N. Budisa, B. Steipe, P. Demange, C. Eckerskorn, J.Kellermann and R. Huber, Eur. J. Biochem., 230:788 (1995); and, N.Budisa, W. Kambrock, S. Steinbacher, A. Humm, L. Prade, T. Neuefeind, L.Moroder and R. Huber, J. Mol. Biol., 270:616 (1997). Methionine analogswith alkene or alkyne functionalities have also been incorporatedefficiently, allowing for additional modification of proteins bychemical means. See, e.g., J. C. M. vanHest and D. A. Tirrell, FEBSLett., 428:68 (1998); J. C. M. van Hest, K. L. Kiick and D. A. Tirrell,J. Am. Chem. Soc., 122:1282 (2000); and, K. L. Kiick and D. A. Tirrell,Tetrahedron, 56:9487 (2000); U.S. Pat. No. 6,586,207; U.S. PatentPublication 2002/0042097, which are incorporated by reference herein.

The success of this method depends on the recognition of the unnaturalamino acid analogs by aminoacyl-tRNA synthetases, which, in general,require high selectivity to insure the fidelity of protein translation.One way to expand the scope of this method is to relax the substratespecificity of aminoacyl-tRNA synthetases, which has been achieved in alimited number of cases. For example, replacement of Ala²⁹⁴ by Gly inEscherichia coli phenylalanyl-tRNA synthetase (PheRS) increases the sizeof substrate binding pocket, and results in the acylation of tRNAPhe byp-Cl-phenylalanine (p-Cl-Phe). See, M. Ibba, P. Kast and H. Hennecke,Biochemistry, 33:7107 (1994). An Escherichia coli strain harboring thismutant PheRS allows the incorporation of p-Cl-phenylalanine orp-Br-phenylalanine in place of phenylalanine. See, e.g., M. Ibba and H.Hennecke, FEBS Lett., 364:272 (1995); and, N. Sharma, R. Furter, P. Kastand D. A. Tirrell, FEBS Lett., 467:37 (2000). Similarly, a pointmutation Phe130Ser near the amino acid binding site of Escherichia colityrosyl-tRNA synthetase was shown to allow azatyrosine to beincorporated more efficiently than tyrosine. See, F. Haman-Takaku, T.Iwama, S. Saito-Yano, K. Takaku, Y. Monden, M. Kitabatake, D. Soil andS. Nishimura, J. Biol. Chem., 275:40324 (2000).

Another strategy to incorporate unnatural amino acids into proteins invivo is to modify synthetases that have proofreading mechanisms. Thesesynthetases cannot discriminate and therefore activate amino acids thatare structurally similar to the cognate natural amino acids. This erroris corrected at a separate site, which deacylates the mischarged aminoacid from the tRNA to maintain the fidelity of protein translation. Ifthe proofreading activity of the synthetase is disabled, structuralanalogs that are misactivated may escape the editing function and beincorporated. This approach has been demonstrated recently with thevalyl-tRNA synthetase (ValRS). See, V. Doring, H. D. Mootz, L. A.Nangle, T. L. Hendrickson, V. de Crecy-Lagard, P. Schimmel and P.Marliere, Science, 292:501 (2001). ValRS can misaminoacylate tRNAValwith Cys, Thr, or aminobutyrate (Abu); these noncognate amino acids aresubsequently hydrolyzed by the editing domain. After random mutagenesisof the Escherichia coli chromosome, a mutant Escherichia coli strain wasselected that has a mutation in the editing site of ValRS. Thisedit-defective ValRS incorrectly charges tRNAVal with Cys. Because Abusterically resembles Cys (—SH group of Cys is replaced with —CH3 inAbu), the mutant ValRS also incorporates Abu into proteins when thismutant Escherichia coli strain is grown in the presence of Abu. Massspectrometric analysis shows that about 24% of valines are replaced byAbu at each valine position in the native protein.

Solid-phase synthesis and semisynthetic methods have also allowed forthe synthesis of a number of proteins containing novel amino acids. Forexample, see the following publications and references cited within,which are as follows: Crick, F. J. C., Barrett, L. Brenner, S.Watts-Tobin, R. General nature of the genetic code for proteins. Nature, 1227-1232 (1961); Hofmann, K., Bohn, H. Studies on polypeptides.XXXVI. The effect of pyrazole-imidazole replacements on the S-proteinactivating potency of an S-peptide fragment, J. Am Chem , 5914-5919(1966); Kaiser, E. T. Synthetic approaches to biologically activepeptides and proteins including enyzmes, Acc Chem Res, 47-54 (1989);Nakatsuka, T., Sasaki, T., Kaiser, E. T. Peptide segment couplingcatalyzed by the semisynthetic enzyme thiosubtilisin, J Am Chem Soc,3808-3810 (1987); Schnolzer, M., Kent, S B H. Constructing proteins bydovetailing unprotected synthetic peptides: backbone-engineered HIVprotease, Science, 221-225 (1992); Chaiken, I. M. Semisynthetic peptidesand proteins, CRC Crit Rev Biochem, 255-301 (1981); Offord, R. E.Protein engineering by chemical means? Protein Eng., 151-157 (1987);and, Jackson, D. Y., Burnier, J., Quan, C., Stanley, M., Tom, J., Wells,J. A. A Designed Peptide Ligase for Total Synthesis of Ribonuclease Awith Unnatural Catalytic Residues, Science, 243 (1994).

Chemical modification has been used to introduce a variety of unnaturalside chains, including cofactors, spin labels and oligonucleotides intoproteins in vitro. See, e.g., Corey, D. R., Schultz, P. G. Generation ofa hybrid sequence-specific single-stranded deoxyribonuclease, Science,1401-1403 (1987); Kaiser, E. T., Lawrence D. S., Rokita, S. E. Thechemical modification of enzymatic specificity, Rev Biochem , 565-595(1985); Kaiser, E. T., Lawrence, D. S. Chemical mutation of enyzmeactive sites, Science, 505-511 (1984); Neet, K. E., Nanci A, Koshland,D. E. Properties of thiol-subtilisin, J Biol. Chem , 6392-6401 (1968);Polgar, L. B., M. L. A new enzyme containing a synthetically formedactive site. Thiol-subtilisin. J. Am Chem Soc, 3153-3154 (1966); and,Pollack, S. J., Nakayama, G. Schultz, P. G. Introduction of nucleophilesand spectroscopic probes into antibody combining sites, Science,1038-1040 (1988).

Alternatively, biosynthetic methods that employ chemically modifiedaminoacyl-tRNAs have been used to incorporate several biophysical probesinto proteins synthesized in vitro. See the following publications andreferences cited within: Brunner, J. New Photolabeling and crosslinkingmethods, Annu. Rev Biochem, 483-514 (1993); and, Krieg, U. C., Walter,P., Hohnson, A. E. Photocrosslinking of the signal sequence of nascentpreprolactin of the 54-kilodalton polypeptide of the signal recognitionparticle, Proc. Natl. Acad. Sci, 8604-8608 (1986).

Previously, it has been shown that unnatural amino acids can besite-specifically incorporated into proteins in vitro by the addition ofchemically aminoacylated suppressor tRNAs to protein synthesis reactionsprogrammed with a gene containing a desired amber nonsense mutation.Using these approaches, one can substitute a number of the common twentyamino acids with close structural homologues, e.g., fluorophenylalaninefor phenylalanine, using strains auxotropic for a particular amino acid.See, e.g., Noren, C. J., Anthony-Cahill, Griffith, M. C., Schultz, P. G.A general method for site-specific incorporation of unnatural aminoacids into proteins, Science, 244: 182-188 (1989); M. W. Nowak, et al.,Science 268:439-42 (1995); Bain, J. D., Glabe, C. G., Dix, T. A.,Chamberlin, A. R., Diala, E. S. Biosynthetic site-specific Incorporationof a non-natural amino acid into a polypeptide, J. Am Chem Soe,111:8013-8014 (1989); N. Budisa et al., FASEB J. 13:41-51 (1999);Elliman, J. A., Mendel, D., Anthony-Cahill, S., Noren, C. J., Schultz,P. G. Biosynthetic method for introducing unnatural amino acidssite-specifically into proteins, Methods in Enz., 301-336 (1992); and,Mendel, D., Cornish, V. W. & Schultz, P. G. Site-Directed Mutagenesiswith an Expanded Genetic Code, Annu Rev Biophys. Biomol Struct. 24,435-62 (1995).

For example, a suppressor tRNA was prepared that recognized the stopcodon UAG and was chemically aminoaeylated with an unnatural amino acid.Conventional site-directed mutagenesis was used to introduce the stopcodon TAG, at the site of interest in the protein gene. See, e.g.,Sayers, J. R., Schmidt, W. Eckstein, F. 5′, 3′ Exonuclease inphosphorothioate-based olignoucleotide-directed mutagensis, NucleicAcids Res, 791-802 (1988). When the acylated suppressor tRNA and themutant gene were combined in an in vitro transcription/translationsystem, the unnatural amino acid was incorporated in response to the UAGcodon which gave a protein containing that amino acid at the specifiedposition. Experiments using [³H]-Phe and experiments with α-hydroxyacids demonstrated that only the desired amino acid is incorporated atthe position specified by the UAG codon and that this amino acid is notincorporated at any other site in the protein. See, e.g., Noren, et al,supra; Kobayashi et al., (2003) Nature Structural Biology 10(6):425-432;and, Ellman, J. A., Mendel, D., Schultz, P. G. Site-specificincorporation of novel backbone structures into proteins, Science,197-200 (1992).

Microinjection techniques have also been use incorporate unnatural aminoacids into proteins. See, e.g., M. W. Nowak, P. C. Kearney, J. R.Sampson, M. E. Saks, C. G. Labarca, S. K. Silverman, W. G. Zhong, J.Thorson, J. N. Abelson, N. Davidson, P. G. Schultz, D. A. Dougherty andH. A. Lester, Science, 268:439 (1995); and, D. A. Dougherty, Curr. Opin.Chem. Biol., 4:645 (2000). A Xenopus oocyte was coinjected with two RNAspecies made in vitro: an mRNA encoding the target protein with a UAGstop codon at the amino acid position of interest and an ambersuppressor tRNA aminoacylated with the desired unnatural amino acid. Thetranslational machinery of the oocyte then inserts the unnatural aminoacid at the position specified by UAG. This method has allowed in vivostructure-function studies of integral membrane proteins, which aregenerally not amenable to in vitro expression systems. Examples includethe incorporation of a fluorescent amino acid into tachykininneurokinin-2 receptor to measure distances by fluorescence resonanceenergy transfer, see, e.g., G. Turcatti, K. Nemeth, M. D. Edgerton, U.Meseth, F. Talabot, M. Peitsch, J. Knowles, H. Vogel and A. Chollet, J.Biol. Chem., 271:19991 (1996); the incorporation of biotinylated aminoacids to identify surface-exposed residues in ion channels, see, e.g.,J. P. Gallivan, H. A. Lester and D. A. Dougherty, Chem. Biol., 4:739(1997); the use of caged tyrosine analogs to monitor conformationalchanges in an ion channel in real time, see, e.g., J. C. Miller, S. K.Silverman, P. M. England, D. A. Dougherty and H. A. Lester, Neuron,20:619 (1998); and, the use of alpha hydroxy amino acids to change ionchannel backbones for probing their gating mechanisms. See, e.g., P. M.England, Y. Zhang, D. A. Dougherty and H. A. Lester, Cell, 96:89 (1999);and, T. Lu, A. Y. Ting, J. Mainland, L. Y. Jan, P. G. Schultz and J.Yang, Nat. Neurosci., 4:239 (2001).

The ability to incorporate unnatural amino acids directly into proteinsin vivo offers the advantages of high yields of mutant proteins,technical ease, the potential to study the mutant proteins in cells orpossibly in living organisms and the use of these mutant proteins intherapeutic treatments. The ability to include unnatural amino acidswith various sizes, acidities, nucleophilicities, hydrophobicities, andother properties into proteins can greatly expand our ability torationally and systematically manipulate the structures of proteins,both to probe protein function and create new proteins or organisms withnovel properties. However, the process is difficult, because the complexnature of tRNA-synthetase interactions that are required to achieve ahigh degree of fidelity in protein translation.

In one attempt to site-specifically incorporate para-F-Phe, a yeastamber suppressor tRNAPheCUA/phenylalanyl-tRNA synthetase pair was usedin a p-F-Phe resistant, Phe auxotrophic Escherichia coli strain. See,e.g., R. Futter, Protein Sci., 7:419 {1998).

It may also be possible to obtain expression of a fEPO polynucleotide ofthe present invention using a cell-free (in-vitro) translational system.In these systems, which can include either mRNA as a template (in-vitrotranslation) or DNA as a template (combined in-vitro transcription andtranslation), the in vitro synthesis is directed by the ribosomes.Considerable effort has been applied to the development of cell-freeprotein expression systems. See, e.g., Kim, D. -M. and J. R. Swartz,Biotechnology and Bioengineering, 74 :309-316 (2001); Kim, D. -M. and J.R. Swartz, Biotechnology Letters, 22, 1537-1542, (2000); Kim, D. -M.,and J. R. Swartz, Biotechnology Progress, 16, 385-390, (2000); Kim, D.-M., and J. R. Swartz, Biotechnology and Bioengineering, 66, 180-188,(1999); and Patnaik, R. and J. R. Swartz, Biotechniques 24, 862-868,(1998); U.S. Pat. No. 6,337,191; U.S. Patent Publication No.2002/0081660; WO 00/55353; WO 90/05785, which are incorporated byreference herein. Another approach that may be applied to the expressionof fEPO polypeptides comprising a non-naturally encoded amino acidinclude the mRNA-peptide fusion technique. See, e.g., R. Roberts and J.Szostak, Proc. Nall Acad. Sci. (USA) 94 12297-12302 (1997); A. Frankel,et al., Chemistry & Biology 10, 1043-1050 (2003). In this approach, anmRNA template linked to puromycin is translated into peptide on theribosome. If one or more tRNA molecules has been modified, non-naturalamino acids can be incorporated into the peptide as well. After the lastmRNA codon has been read, puromycin captures the C-terminus of thepeptide. If the resulting mRNA-peptide conjugate is found to haveinteresting properties in an in vitro assay, its identity can be easilyrevealed from the mRNA sequence. In this way, one may screen librariesof fEPO polypeptides comprising one or more non-naturally encoded aminoacids to identify polypeptides having desired properties. More recently,in vitro ribosome translations with purified components have beenreported that permit the synthesis of peptides substituted withnon-naturally encoded amino acids. See, e.g., A. Forster et al., Proc.Natl Acad. Sci. (USA) 100 6353 (2003).

X Macromolecular Polymers Coupled to fEPO

A wide variety of macromolecular polymers and other molecules can belinked to fEPO polypeptides of the present invention to modulatebiological properties of fEPO, and/or provide new biological propertiesto the fEPO molecule. These macromolecular polymers can be linked tofEPO via a naturally encoded amino acid, via a non-naturally enecodedamio acid, or any functional substituent of a natural or non-naturalamino acid, or any substituent or functional group added to a natural ornon-natural amino acid.

The present invention provides substantially homogenous preparations ofpolymer:protein conjugates. “Substantially homogenous” as used hereinmeans that polymer:protein conjugate molecules are observed to begreater than half of the total protein. The polymer:protein conjugatehas biological activity and the present “substantially homogenous”PEGylated fEPO preparations provided herein are those which arehomogenous enough to display the advantages of a homogenous preparation,e.g., ease in clinical application in predictability of lot to lotpharmacokinetics.

One may also choose to prepare a mixture of polymer:protein conjugatemolecules, and the advantage provided herein is that one may select theproportion of mono-polymer:protein conjugate to include in the mixture.Thus, if desired, one may prepare a mixture of various proteins withvarious numbers of polymer moieties attached (i.e., di-, tri-, tetra-,etc.) and combine said conjugates with the mono-polymer:proteinconjugate prepared using the methods of the present invention, and havea mixture with a predeteduined proportion of mono-polymer:proteinconjugates.

The polymer selected may be water soluble so that the protein to whichit is attached does not precipitate in an aqueous environment, such as aphysiological environment. The polymer may be branched or unbranched.Preferably, for therapeutic use of the end-product preparation, thepolymer will be pharmaceutically acceptable.

The proportion of polyethylene glycol molecules to protein moleculeswill vary, as will their concentrations in the reaction mixture. Ingeneral, the optimum ratio (in terms of efficiency of reaction in thatthere is minimal excess unreacted protein or polymer) may be determinedby the molecular weight of the polyethylene glycol selected and on thenumber of available reactive groups available. As relates to molecularweight, typically the higher the molecular weight of the polymer, thefewer number of polymer molecules which may be attached to the protein.Similarly, branching of the polymer should be taken into account whenoptimizing these parameters. Generally, the higher the molecular weight(or the more branches) the higher the polymer:protein ratio.

As used herein, and when contemplating PEG:fEPO conjugates, the term“therapeutically effective amount” refers to an amount which gives anincrease in hematocrit that provides benefit to a patient. The amountwill vary from one individual to another and will depend upon a numberof factors, including the overall physical condition of the patient andthe underlying cause of anemia. For example, a therapeutically effectiveamount of fEPO for a patient suffering from chronic renal failure is 50to 150 units/kg three times per week. The amount of fEPO used fortherapy gives an acceptable rate of hematocrit increase and maintainsthe hematocrit at a beneficial level (usually at least about 30% andtypically in a range of 30% to 36%). A therapeutically effective amountof the present compositions may be readily ascertained by one skilled inthe art using publicly available materials and procedures.

The water soluble polymer may be any structural form including but notlimited to linear, forked or branched. Typically, the water solublepolymer is a poly(alkylene glycol), such as poly(ethylene glycol) (PEG),but other water soluble polymers can also be employed. By way ofexample, PEG is used to describe certain embodiments of this invention.

PEG is a well-known, water soluble polymer that is commerciallyavailable or can be prepared by ring-opening polymerization of ethyleneglycol according to methods well known in the art (Sandler and Karo,Polymer Synthesis, Academic Press, New York, Vol. 3, pages 138-161). Theterm “PEG” is used broadly to encompass any polyethylene glycolmolecule, without regard to size or to modification at an end of thePEG, and can be represented as linked to fEPO by the formula:

XO—(CH₂CH₂O)_(n)—CH₂CH₂—Y

where n is 2 to 10,000 and X is H or a terminal modification, includingbut not limited to, a C₁₋₄ alkyl.

In some cases, a PEG used in the invention terminates on one end withhydroxy or methoxy, i.e., X is H or CH₃ (“methoxy PEG”). Alternatively,the PEG can terminate with a reactive group, thereby forming abifunctional polymer. Typical reactive groups can include those reactivegroups that are commonly used to react with the functional groups foundin the 20 common amino acids (including but not limited to, maleimidegroups, activated carbonates (including but not limited to,p-nitrophenyl ester), activated esters (including but not limited to,N-hydroxysuccinimide, p-nitrophenyl ester) and aldehydes) as well asfunctional groups that are inert to the 20 common amino acids but thatreact specifically with complementary functional groups present innon-naturally encoded amino acids (including but not limited to, azidegroups, alkyne groups). It is noted that the other end of the PEG, whichis shown in the above formula by Y, will attach either directly orindirectly to a fEPO polypeptide via a naturally-occurring ornon-naturally encoded amino acid. For instance, Y may be an amide,carbamate or urea linkage to an amine group (including but not limitedto, the epsilon amine of lysine or the N-terminus) of the polypeptide.Alternatively, Y may be a maleimide linkage to a thiol group (includingbut not limited to, the thiol group of cysteine). Alternatively, Y maybe a linkage to a residue not commonly accessible via the 20 commonamino acids. For example, an azide group on the PEG can be reacted withan alkyne group on the fEPO polypeptide to form a Huisgen [3+2]cycloaddition product. Alternatively, an alkyne group on the PEG can bereacted with an azide group present in a non-naturally encoded aminoacid to form a similar product. In some embodiments, a strongnucleophile (including but not limited to, hydrazine, hydrazide,hydroxylamine, semicarbazide) can be reacted with an aldehyde or ketonegroup present in a non-naturally encoded amino acid to form a hydrazone,oxime or semicarbazone, as applicable, which in some cases can befurther reduced by treatment with an appropriate reducing agent.Alternatively, the strong nucleophile can be incorporated into the fEPOpolypeptide via a non-naturally encoded amino acid and used to reactpreferentially with a ketone or aldehyde group present in the watersoluble polymer.

Any molecular mass for a PEG can be used as practically desired,including but not limited to, from about 1,000 Daltons (Da) to 100,000Da or more as desired (including but not limited to, sometimes 1-50 kDaor 10-40 kDa). Branched chain PEGs, including but not limited to, PEG'swith each chain having a MW ranging from 10-40 kDa (including but notlimited to, 5-20 kDa) can also be used. A wide range of PEG moleculesare described in, including but not limited to, the Shearwater Polymers,Inc. catalog, Nektar Theraoeutics catalog, incorporated herein byreference.

Generally, at least one terminus of the PEG molecule is available forreaction with the non-naturally-encoded amino acid. For example, PEGderivatives bearing alkyne and azide moieties for reaction with aminoacid side chains can be used to attach PEG to non-naturally encodedamino acids as described herein. If the non-naturally encoded amino acidcomprises an azide, then the PEG will typically contain either an alkynemoiety to effect formation of the [3+2] cycloaddition product or anactivated PEG species (i.e., ester, carbonate) containing a phosphinegroup to effect formation of the amide linkage. Alternatively, if thenon-naturally encoded amino acid comprises an alkyne, then the PEG willtypically contain an azide moiety to effect formation of the [3+2]Huisgen cycloaddition product. If the non-naturally encoded amino acidcomprises a carbonyl group, the PEG will typically comprise a potentnucleophile (including but not limited to, a hydrazide, hydroxylamine orsemicarbazide functionality) in order to effect formation ofcorresponding hydrazone, oxime, and semicarbazone linkages,respectively. In other alternatives, a reverse of the orientation of thereactive groups described above can be used, i.e., an azide moiety inthe non-naturally encoded amino acid can be reacted with a PEGderivative containing an alkyne.

In some embodiments, the fEPO variant with a PEG derivative contains achemical functionality that is reactive with the chemical functionalitypresent on the side chain of the non-naturally encoded amino acid.

The invention provides in some embodiments azide- andacetylene-containing polymer derivatives comprising a water solublepolymer backbone having an average molecular weight from about 800 Da toabout 100,000 Da. The polymer backbone of the water-soluble polymer canbe poly(ethylene glycol). However, it should be understood that a widevariety of water soluble polymers including but not limited topoly(ethylene)glycol and other related polymers, including poly(dextran)and polypropylene glycol), are also suitable for use in the practice ofthis invention and that the use of the term PEG or poly(ethylene glycol)is intended to encompass and include all such molecules. The term PEGincludes, but is not limited to, poly(ethylene glycol) in any of itsforms, including bifunctional PEG, multiarmed PEG, derivatized PEG,forked PEG, branched PEG, pendent PEG (i.e. PEG or related polymershaving one or more functional groups pendent to the polymer backbone),or PEG with degradable linkages therein.

PEG is typically clear, colorless, odorless, soluble in water, stable toheat, inert to many chemical agents, does not hydrolyze or deteriorate,and is generally non-toxic. Poly(ethylene glycol) is considered to bebiocompatible, which is to say that PEG is capable of coexistence withliving tissues or organisms without causing harm. More specifically, PEGis substantially non-immunogenic, which is to say that PEG does not tendto produce an immune response in the body. When attached to a moleculehaving some desirable function in the body, such as a biologicallyactive agent, the PEG tends to mask the agent and can reduce oreliminate any immune response so that an organism can tolerate thepresence of the agent. PEG conjugates tend not to produce a substantialimmune response or cause clotting or other undesirable effects. PEGhaving the formula —CH₂CH₂O—(CH₂CH₂O)_(n)—CH₂CH₂—, where n is from about3 to about 4000, typically from about 20 to about 2000, is suitable foruse in the present invention. PEG having a molecular weight of fromabout 800 Da to about 100,000 Da are in some embodiments of the presentinvention particularly useful as the polymer backbone.

The polymer backbone can be linear or branched. Branched polymerbackbones are generally known in the art. Typically, a branched polymerhas a central branch core moiety and a plurality of linear polymerchains linked to the central branch core. PEG is commonly used inbranched forms that can be prepared by addition of ethylene oxide tovarious polyols, such as glycerol, glycerol oligomers, pentaerythritoland sorbitol. The central branch moiety can also be derived from severalamino acids, such as lysine. The branched poly(ethylene glycol) can berepresented in general form as R(-PEG-OH)_(m) in which R is derived froma core moiety, such as glycerol, glycerol oligomers, or pentaerythritol,and in represents the number of arms. Multi-armed PEG molecules, such asthose described in U.S. Pat. Nos. 5,932,462 5,643,575; 5,229,490;4,289,872; U.S. Pat. Appl. 2003/0143596; WO 96/21469; and WO 93/21259,each of which is incorporated by reference herein in its entirety, canalso be used as the polymer backbone.

Branched PEG can also be in the form of a forked PEG represented byPEG(-YCHZ₂)_(n), where Y is a linking group and Z is an activatedterminal group linked to CH by a chain of atoms of defined length.

Yet another branched form, the pendant PEG, has reactive groups, such ascarboxyl, along the PEG backbone rather than at the end of PEG chains.

In addition to these forms of PEG, the polymer can also be prepared withweak or degradable linkages in the backbone. For example, PEG can beprepared with ester linkages in the polymer backbone that are subject tohydrolysis. As shown below, this hydrolysis results in cleavage of thepolymer into fragments of lower molecular weight:

-PEG-CO₂-PEG-+H₂O→PEG-CO₂H+HO-PEG-

It is understood by those skilled in the art that the term poly(ethyleneglycol) or PEG represents or includes all the forms known in the artincluding but not limited to those disclosed herein.

Many other polymers are also suitable for use in the present invention.In some embodiments, polymer backbones that are water-soluble, with from2 to about 300 termini, are particularly useful in the invention.Examples of suitable polymers include, but are not limited to, otherpoly(alkylene glycols), such as poly(propylene glycol) (“PPG”),copolymers thereof (including but not limited to copolymers of ethyleneglycol and propylene glycol), terpolymers thereof, mixtures thereof, andthe like. Although the molecular weight of each chain of the polymerbackbone can vary, it is typically in the range of from about 800 Da toabout 100,000 Da, often from about 6,000 Da to about 80,000 Da.

Those of ordinary skill in the art will recognize that the foregoinglist for substantially water soluble backbones is by no means exhaustiveand is merely illustrative, and that all polymeric materials having thequalities described above are contemplated as being suitable for use inthe present invention.

In some embodiments of the present invention the polymer derivatives are“multi-functional”, meaning that the polymer backbone has at least twotermini, and possibly as many as about 300 termini, functionalized oractivated with a functional group. Multifunctional polymer derivativesinclude, but are not limited to, linear polymers having two termini,each terminus being bonded to a functional group which may be the sameor different.

In one embodiment, the polymer derivative has the structure:

X-A-POLY-B—N═N═N

wherein:

-   N═N═N is an azide moiety;-   B is a linking moiety, which may be present or absent;-   POLY is a water-soluble non-antigenic polymer;-   A is a linking moiety, which may be present or absent and which may    be the same as B or different; and-   X is a second functional group.

Examples of a linking moiety for A and B include, but are not limitedto, a multiply-functionalized alkyl group containing up to 18, and morepreferably between 1-10 carbon atoms. A heteroatom such as nitrogen,oxygen or sulfur may be included with the alkyl chain. The alkyl chainmay also be branched at a heteroatom. Other examples of a linking moietyfor A and B include, but are not limited to, a multiply functionalizedaryl group, containing up to 10 and more preferably 5-6 carbon atoms.The aryl group may be substituted with one more carbon atoms, nitrogen,oxygen or sulfur atoms. Other examples of suitable linking groupsinclude those linking groups described in U.S. Pat. Nos. 5,932,462 and5,643,575; and U.S. Pat. Appl. Publication 2003/0143596, each of whichis incorporated by reference herein in its entirety. Those of ordinaryskill in the art will recognize that the foregoing list for linkingmoieties is by no means exhaustive and is merely illustrative, and thatall linking moieties having the qualities described above arecontemplated to be suitable for use in the present invention.

Examples of suitable functional groups for use as X include, but are notlimited to, hydroxyl, protected hydroxyl, alkoxyl, active ester, such asN-hydroxysuccinimidyl esters and 1-benzotriazolyl esters, activecarbonate, such as N-hydroxysuccinimidyl carbonates and 1-benzotriazolylcarbonates, acetal, aldehyde, aldehyde hydrates, alkenyl, acrylate,methacrylate, acrylamide, active sulfonc, amine, aminooxy, protectedamine, hydrazide, protected hydrazide, protected thiol, carboxylic acid,protected carboxylic acid, isocyanate, isothiocyanate, maleimide,vinylsulfone, dithiopyridine, vinylpyridine, iodoacetamide, epoxide,glyoxals, diones, mesylates, tosylates, tresylate, alkene, ketone, andazide. As is understood by those skilled in the art, the selected Xmoiety should be compatible with the azide group so that reaction withthe azide group does not occur. The azide-containing polymer derivativesmay be homobifunctional, meaning that the second functional group (i.e.,X) is also an azide moiety, or heterobifunctional, meaning that thesecond functional group is a different functional group.

The term “protected” refers to the presence of a protecting group ormoiety that prevents reaction of the chemically reactive functionalgroup under certain reaction conditions. The protecting group will varydepending on the type of chemically reactive group being protected. Forexample, if the chemically reactive group is an amine or a hydrazide,the protecting group can be selected from the group oftert-butyloxycarbonyl (t-Boc) and 9-fluorenylmethoxycarbonyl (Fmoc). Ifthe chemically reactive group is a thiol, the protecting group can beorthopyridyldisulfide. If the chemically reactive group is a carboxylicacid, such as butanoic or propionic acid, or a hydroxyl group, theprotecting group can be benzyl or an alkyl group such as methyl, ethyl,or tert-butyl. Other protecting groups known in the art may also be usedin the present invention.

Specific examples of terminal functional groups in the literatureinclude, but are not limited to, N-succinimidyl carbonate (see e.g.,U.S. Pat. Nos. 5,281,698; 5,468,478), amine (see, e.g., Buckmann et al.Makromol. Chem. 182:1379 (1981), Zaplipsky et al. Eur. Polym. J. 19:1177(1983)), hydrazide (See, e.g., Andresz et al. Makromol. Chem. 179:301(1978)), succinimidyl propionate and succinimidyl butanoate (see, e.g.,Olson et al. in Poly(ethylene glycol) Chemistry & BiologicalApplications, pp 170-181, Harris & Zaplipsky Eds., ACS, Washington,D.C., 1997; see also U.S. Pat. No. 5,672,662), succinimidyl succinate(See, e.g., Abuchowski et al. Cancer Biochem. Biophys. 7:175 (1984) andJoppich et al. Macrolol. Chem. 180:1381 (1979), succinimidyl ester (see,e.g., U.S. Pat. No. 4,670,417), benzotriazole carbonate (see, e.g., U.S.Pat. No. 5,650,234), glycidyl ether (see, e.g., Pitha et al. Eur. JBiochem. 94:11 (1979), Elling et al., Biotech. Appl. Biochem. 13:354(1991), oxycarbonylimidazole (see, e.g., Beauchamp, et al., Anal.Biochem. 131:25 (1983), Tondelli et al. J. Controlled Release 1:251(1985)), p-nitrophenyl carbonate (see, e.g., Veronese, et al., Appl.Biochem. Biotech., 11: 141 (1985); and Sartore et al., Appl. Biochem.Biotech., 27:45 (1991)), aldehyde (see, e.g., Harris et al. J. Polym.Sci. Chem. Ed. 22:341 (1984), U.S. Pat. No. 5,824,784, U.S. Pat. No.5,252,714), maleimide (see, e.g., Goodson et al. Bio/Technology 8:343(1990), Romani et al. in Chemistry of Peptides and Proteins 2:29(1984)), and Kogan, Synthetic Comm. 22:2417 (1992)),orthopyridyl-disulfide (see, e.g., Woghiren, et al. Bioconj. Chem.4:314(1993)), acrylol (see, e.g., Sawhney et al., Macromolecules, 26:581(1993)), vinylsulfone (see, e.g., U.S. Pat. No. 5,900,461). All of theabove references are incorporated herein by reference.

In certain embodiments of the present invention, the polymer derivativesof the invention comprise a polymer backbone having the structure:

X—CH₂CH₂O—(CH₂CH₂O)n-CH₂CH₂—N═N═N

wherein:

-   X is a functional group as described above; and-   n is about 20 to about 4000.

In another embodiment, the polymer derivatives of the invention comprisea polymer backbone having the structure:

X—CH₂CH₂O—(CH₂CH₂O)n-CH₂CH₂—O—(CH₂)_(m)—W—N═N═N

wherein:

-   W is an aliphatic or aromatic linker moiety comprising between 1-10    carbon atoms;-   n is about 20 to about 4000; and-   X is a functional group as described above.

The azide-containing PEG derivatives of the invention can be prepared bya variety of methods known in the art and/or disclosed herein. In onemethod, shown below, a water soluble polymer backbone having an averagemolecular weight from about 800 Da to about 100,000 Da, the polymerbackbone having a first terminus bonded to a first functional group anda second terminus bonded to a suitable leaving group, is reacted with anazide anion (which may be paired with any of a number of suitablecounter-ions, including sodium, potassium, tert-butylammonium and soforth). The leaving group undergoes a nucleophilic displacement and isreplaced by the azide moiety, affording the desired azide-containing PEGpolymer.

X-PEG-L+N₃ ⁻→X-PEG-N₃

As shown, a suitable polymer backbone for use in the present inventionhas the formula X-PEG-L, wherein PEG is poly(ethylene glycol) and X is afunctional group which does not react with azide groups and L is asuitable leaving group. Examples of suitable functional groups include,but are not limited to, hydroxyl, protected hydroxyl, acetal, alkenyl,amine, aminooxy, protected amine, protected hydrazide, protected thiol,carboxylic acid, protected carboxylic acid, maleimide, dithiopyridine,and vinylpyridine, and ketone. Examples of suitable leaving groupsinclude, but are not limited to, chloride, bromide, iodide, mesylate,tresylate, and tosylate.

In another method for preparation of the azide-containing polymerderivatives of the present invention, a linking agent bearing an azidefunctionality is contacted with a water soluble polymer backbone havingan average molecular weight from about 800 Da to about 100,000 Da,wherein the linking agent bears a chemical functionality that will reactselectively with a chemical functionality on the PEG polymer, to form anazide-containing polymer derivative product wherein the azide isseparated from the polymer backbone by a linking group.

An exemplary reaction scheme is shown below:

X-PEG-M+N-linker-N═N═N PG-X-PEG-linker-N═N═N

wherein:

-   PEG is poly(ethylene glycol) and X is a capping group such as alkoxy    or a functional group as described above; and-   M is a functional group that is not reactive with the azide    functionality but that will react efficiently and selectively with    the N functional group.

Examples of suitable functional groups include, but are not limited to,M being a carboxylic acid, carbonate or active ester if N is an amine; Mbeing a ketone if N is a hydrazide or aminooxy moiety; M being a leavinggroup if N is a nucleophile.

Purification of the crude product may be accomplished by known methodsincluding, but are not limited to, precipitation of the product followedby chromatography, if necessary.

A more specific example is shown below in the case of PEG diamine, inwhich one of the amines is protected by a protecting group moiety suchas tert-butyl-Boc and the resulting mono-protected PEG diamine isreacted with a linking moiety that bears the azide functionality:

BocHN-PEG-NH₂+HO₂C—(CH₂)₃—N═N═N

In this instance, the amine group can be coupled to the carboxylic acidgroup using a variety of activating agents such as thionyl chloride orcarbodiimide reagents and N-hydroxysuccinimide or N-hydroxybenzotriazoleto create an amide bond between the monoamine PEG derivative and theazide-bearing linker moiety. After successful formation of the amidebond, the resulting N-tert-butyl-Boc-protected azide-containingderivative can be used directly to modify bioactive molecules or it canbe further elaborated to install other useful functional groups. Forinstance, the N-t-Boc group can be hydrolyzed by treatment with strongacid to generate an omega-amino-PEG-azide. The resulting amine can beused as a synthetic handle to install other useful functionality such asmaleimide groups, activated disulfides, activated esters and so forthfor the creation of valuable heterobifunetional reagents.

Heterobifunctional derivatives are particularly useful when it isdesired to attach different molecules to each tcnninus of the polymer.For example, the omega-N-amino-N-azido PEG would allow the attachment ofa molecule having an activated electrophilic group, such as an aldehyde,ketone, activated ester, activated carbonate and so forth, to oneterminus of the PEG and a molecule having an acetylene group to theother terminus of the PEG.

In another embodiment of the invention, the polymer derivative has thestructure:

X-A-POLY-B—C≡C—R

wherein:

-   R can be either H or an alkyl, alkene, alkyoxy, or aryl or    substituted aryl group;-   B is a linking moiety, which may be present or absent;-   POLY is a water-soluble non-antigenic polymer;-   A is a linking moiety, which may be present or absent and which may    be the same as B or different; and-   X is a second functional group.

Examples of a linking moiety for A and B include, but are not limitedto, a multiply-functionalized alkyl group containing up to 18, and morepreferably between 1-10 carbon atoms. A heteroatom such as nitrogen,oxygen or sulfur may be included with the alkyl chain. The alkyl chainmay also be branched at a heteroatom. Other examples of a linking moietyfor A and B include, but are not limited to, a multiply functionalizedaryl group, containing up to 10 and more preferably 5-6 carbon atoms.The aryl group may be substituted with one more carbon atoms, nitrogen,oxygen or sulfur atoms. Other examples of suitable linking groupsinclude those linking groups described in U.S. Pat. Nos. 5,932,462 and5,643,575 and U.S. Pat. Appl. 2003/0143596, each of which isincorporated by reference herein in its entirety. Those of ordinaryskill in the art will recognize that the foregoing list for linkingmoieties is by no means exhaustive and is intended to be merelyillustrative, and that a wide variety of linking moieties having thequalities described above are contemplated to be useful in the presentinvention.

Examples of suitable functional groups for use as X include hydroxyl,protected hydroxyl, alkoxyl, active ester, such as N-hydroxysuccinimidylesters and 1-benzotriazolyl esters, active carbonate, such asN-hydroxysuccinimidyl carbonates and 1-benzotriazolyl carbonates,acetal, aldehyde, aldehyde hydrates, alkenyl, acrylate, methacrylate,acrylamide, active sulfone, amine, aminooxy, protected amine, hydrazide,protected hydrazide, protected thiol, carboxylic acid, protectedcarboxylic acid, isocyanate, isothiocyanate, maleimide, vinylsulfone,dithiopyridine, vinylpyridine, iodoacetamide, epoxide, glyoxals, diones,mesylates, tosylates, and tresylate, alkene, ketone, and acetylene. Aswould be understood, the selected X moiety should be compatible with theacetylene group so that reaction with the acetylene group does notoccur. The acetylene-containing polymer derivatives may behomobifunctional, meaning that the second functional group (i.e., X) isalso an acetylene moiety, or heterobifunctional, meaning that the secondfunctional group is a different functional group.

In another embodiment of the present invention, the polymer derivativescomprise a polymer backbone having the structure:

X—CH₂CH₂O—(CH₂CH₂O)n-CH₂CH₂—O—(CH₂)_(m)—C≡CH

wherein:

-   X is a functional group as described above;-   n is about 20 to about 4000; and-   m is between 1 and 10.    Specific examples of each of the heterobifunctional PEG polymers are    shown below.

The acetylene-containing PEG derivatives of the invention can beprepared using methods known to those skilled in the art and/ordisclosed herein. In one method, a water soluble polymer backbone havingan average molecular weight from about 800 Da to about 100,000 Da, thepolymer backbone having a first terminus bonded to a first functionalgroup and a second terminus bonded to a suitable nucleophilic group, isreacted with a compound that bears both an acetylene functionality and aleaving group that is suitable for reaction with the nucleophilic groupon the PEG. When the PEG polymer bearing the nucleophilic moiety and themolecule bearing the leaving group are combined, the leaving groupundergoes a nucleophilic displacement and is replaced by thenucleophilic moiety, affording the desired acetylene-containing polymer.

X-PEG-Nu+L-A-C→X-PEG-Nu-A-C≡CR′

As shown, a preferred polymer backbone for use in the reaction has theformula X-PEG-Nu, wherein PEG is poly(ethylene glycol), Nu is anucleophilic moiety and X is a functional group that does not react withNu, L or the acetylene functionality.

Examples of Nu include, but are not limited to, amine, alkoxy, aryloxy,sulfhydryl, imino, carboxylate, hydrazide, aminoxy groups that wouldreact primarily via a SN2-type mechanism. Additional examples of Nugroups include those functional groups that would react primarily via annucleophilic addition reaction. Examples of L groups include chloride,bromide, iodide, mesylate, tresylate, and tosylate and other groupsexpected to undergo nucleophilic displacement as well as ketones,aldehydes, thioesters, olefins, alpha-beta unsaturated carbonyl groups,carbonates and other electrophilic groups expected to undergo additionby nucleophiles.

In another embodiment of the present invention, A is an aliphatic linkerof between 1-10 carbon atoms or a substituted aryl ring of between 6-14carbon atoms. X is a functional group which does not react with azidegroups and L is a suitable leaving group

In another method for preparation of the acetylene-containing polymerderivatives of the invention, a PEG polymer having an average molecularweight from about 800 Da to about 100,000 Da, bearing either a protectedfunctional group or a capping agent at one terminus and a suitableleaving group at the other terminus is contacted by an acetylene anion.

An exemplary reaction scheme is shown below:

X-PEG-L+-C≡CR′→X-PEG-C≡CR′

wherein:

-   PEG is poly(ethylene glycol) and X is a capping group such as alkoxy    or a functional group as described above; and-   R′ is either H, an alkyl, alkoxy, aryl or aryloxy group or a    substituted alkyl, alkoxyl, aryl or aryloxy group.

In the example above, the leaving group L should be sufficientlyreactive to undergo SN2-type displacement when contacted with asufficient concentration of the acetylene anion. The reaction conditionsrequired to accomplish SN2 displacement of leaving groups by acetyleneanions are well known in the art.

Purification of the crude product can usually be accomplished by methodsknown in the art including, but are not limited to, precipitation of theproduct followed by chromatography, if necessary.

Water soluble polymers can be linked to the fEPO polypeptides of theinvention. The water soluble polymers may be linked via a non-naturallyencoded amino acid incorporated in the fEPO polypeptide or anyfunctional group or substituent of a non-naturally encoded or naturallyencoded amino acid, or any functional group or substituent added to anon-naturally encoded or naturally encoded amino acid. Alternatively,the water soluble polymers are linked to a fEPO polypeptideincorporating a non-naturally encoded amino acid via anaturally-occurring amino acid (including but not limited to, cysteine,lysine or the amine group of the N-terminal residue). In some cases, thefEPO polypeptides of the invention comprise 1, 2, 3, 4, 5, 6, 7, 8, 9,10, wherein one or more non-naturally-encoded amino acid(s) linked towater soluble polymer(s) (including but not limited to, PEG and/oroligosaccharides). In some cases, the fEPO polypeptides of the inventionfurther comprise 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or morenaturally-encoded amino acid(s) linked to water soluble polymers. Insome cases, the fEPO polypeptides of the invention comprise one or morenon-naturally encoded amino acid(s) linked to water soluble polymers andone or more naturally-occurring amino acids linked to water solublepolymers. In some embodiments, the water soluble polymers used in thepresent invention enhance the serum half-life of the fEPO polypeptiderelative to the unconjugated form.

The number of water soluble polymers linked to a fEPO polypeptide (i.e.,the extent of PEGylation or glycosylation) of the present invention canbe adjusted to provide an altered (including but not limited to,increased or decreased) pharmacologic, pharmacokinetic orpharmacodynamic characteristic such as in vivo half-life. In someembodiments, the half-life of fEPO is increased at least about 10, 20,30, 40, 50, 60, 70, 80, 90 percent, two fold, five-fold, 10-fold,50-fold, or at least about 100-fold over an unmodified polypeptide.

PEG Derivatives Containing a Strong Nucleophilic Group (i.e., Hydrazide,Hydrazine, Hydroxylamine or Semicarbazide)

In one embodiment of the present invention, a fEPO polypeptidecomprising a carbonyl-containing non-naturally encoded amino acid ismodified with a PEG derivative that contains a terminal hydrazine,hydroxylamine, hydrazide or semicarbazide moiety that is linked directlyto the PEG backbone.

In some embodiments, the hydroxylamine-terminal PEG derivative will havethe structure:

RO—(CH₂CH₂O)_(n)—O—(CH₂)_(m)—O—NH₂

where R is a simple alkyl (methyl, ethyl, propyl, etc.), m is 2-10 and nis 100-1,000 (i.e., average molecular weight is between 5-40 kDa).

In some embodiments, the hydrazine- or hydrazide-containing PEGderivative will have the structure:

RO—(CH₂CH₂O)_(n)—O—(CH₂)_(n)—X—NH—NH₂

where R is a simple alkyl (methyl, ethyl, propyl, etc.), m is 2-10 and nis 100-1,000 and X is optionally a carbonyl group (C═O) that can bepresent or absent.

In some embodiments, the semicarbazide-containing PEG derivative willhave the structure:

RO—(CH₂CH₂O)_(n)—O—(CH₂)_(m)—NH—C(O)—NH—NH₂

where R is a simple alkyl (methyl, ethyl, propyl, etc.), m is 2-10 and nis 100-1,000.

In another embodiment of the invention, a fEPO polypeptide comprising acarbonyl-containing amino acid is modified with a PEG derivative thatcontains a terminal hydroxylamine, hydrazide or semicarbazide moietythat is linked to the PEG backbone by means of an amide linkage.

In some embodiments, the hydroxylamine-terminal PEG derivatives have thestructure:

RO—(CH₂CH₂O)_(n)—O—(CH₂)₂—NH—C(O)(CH₂)_(m)—O—NH₂

where R is a simple alkyl (methyl, ethyl, propyl, etc.), m is 2-10 and nis 100-1,000 (i.e., average molecular weight is between 5-40 kDa).

In some embodiments, the hydrazine- or hydrazide-containing PEGderivatives have the structure:

RO—(CH₂CH₂O)_(n)—O—(CH₂)₂—NH—C(O)(CH₂)_(m)—X—NH—NH₂

where R is a simple alkyl (methyl, ethyl, propyl, etc.), m is 2-10, n is100-1,000 and X is optionally a carbonyl group (C═O) that can be presentor absent.

In some embodiments, the semicarbazide-containing PEG derivatives havethe structure:

RO—(CH₂CH₂O)_(n)—O—(CH₂)₂—NH—C(O)(CH₂)_(m)—NH—C(O)—NH—NH₂

where R is a simple alkyl (methyl, ethyl, propyl, etc.), m is 2-10 and nis 100-1,000.

In another embodiment of the invention, a fEPO polypeptide comprising acarbonyl-containing amino acid is modified with a branched PEGderivative that contains a terminal hydrazine, hydroxylamine, hydrazideor semicarbazide moiety, with each chain of the branched PEG having a MWranging from 10-40 kDa and, more preferably, from 5-20 kDa.

In another embodiment of the invention, a fEPO polypeptide comprising anon-naturally encoded amino acid is modified with a PEG derivativeshaving a branched structure.

For instance, in some embodiments, the hydrazine- or hydrazide-terminalPEG derivative will have the following structure:

[RO—(CH₂CH₂O)_(n)—O—(CH₂)₂—NH—C(O)]₂CH(CH₂)_(m)—X—NH—NH₂

where R is a simple alkyl (methyl, ethyl, propyl, etc.), m is 2-10 and nis 100-1,000, and X is optionally a carbonyl group (C═O) that can bepresent or absent.

In some embodiments, the PEG derivatives containing a semicarbazidegroup will have the structure:

[RO—(CH₂CH₂O)_(n)—O—(CH₂)₂—C(O)—NH—CH₂—CH₂]₂CH—X—(CH₂)_(m)—NH—C(O)—NH—NH₂

where R is a simple alkyl (methyl, ethyl, propyl, etc.), X is optionallyNH, O, S, C(O) or not present, m is 2-10 and n is 100-1,000.

In some embodiments, the PEG derivatives containing a hydoxylamine groupwill have the structure:

[RO—(CH₂CH₂O)_(n)—O—(CH₂)₂—C(O)—NH—CH₂—CH₂]₂CH—X—(CH₂)_(m)—O—NH₂

where R is a simple alkyl (methyl, ethyl, propyl, etc.), X is optionallyNH, O, S, C(O) or not present, m is 2-10 and n is 100-1,000.

The degree and sites at which the water soluble polymer(s) are linked tofEPO can modulate the binding of fEPO to the fEPO receptor at Site 1. Insome embodiments, the linkages are arranged such that the fEPOpolypeptide binds the fEPO receptor at Site 1 with a K_(d) of about 400nM or lower, with a K_(d) of 150 nM or lower, and in some cases with aK_(d) of 100 nM or lower, as measured by an equilibrium binding assay,such as that described in Spencer et al., J. Biol. Chem., 263:7862-7867(1988).

Methods and chemistry for activation of polymers as well as forconjugation of peptides are described in the literature and are known inthe art. Commonly used methods for activation of polymers include, butare not limited to, activation of functional groups with cyanogenbromide, periodate, glutaraldehyde, biepoxides, epichlorohydrin,divinylsulfone, carbodiimide, sulfonyl halides, trichlorotriazine, etc.(see, R. F. Taylor, (1991), PROTEIN IMMOBILISATION, FUNDAMENTAL ANDAPPLICATIONS, Marcel Dekker, N.Y.; S. S. Wong, (1992), CHEMISTRY OFPROTEIN CONJUGATION AND CROSSLINKING, CRC Press, Boca Raton; G. T.Hermanson et al., (1993), IMMOBILIZED AFFINITY LIGAND TECHNIQUES,Academic Press, N.Y.; Dunn, R. L., et al., Eds. POLYMERIC DRUGS AND DRUGDELIVERY SYSTEMS, ACS Symposium Series Vol. 469, American ChemicalSociety, Washington, D.C. 1991).

Several reviews and monographs on the functionalization and conjugationof PEG are available. See, for example, Harris, Macronol. Chem. Phys.C25: 325-373 (1985); Scouten, Methods in Enzymology 135: 30-65 (1987);Wong et al., Enzyme Microb. Technol. 14: 866-874 (1992); Delgado et al.,Critical Reviews in Therapeutic Drug Carrier Systems 9: 249-304 (1992);Zalipsky, Bioconjugate Chem. 6: 150-165 (1995).

Methods for activation of polymers can also be found in WO 94/17039,U.S. Pat. No. 5,324,844, WO 94/18247, WO 94/04193, U.S. Pat. No.5,219,564, U.S. Pat. No. 5,122,614, WO 90/13540, U.S. Pat. No.5,281,698, and more WO 93/15189, and for conjugation between activatedpolymers and enzymes including but not limited to Coagulation FactorVIII (WO 94/15625), haemoglobin (WO 94/09027), oxygen carrying molecule(U.S. Pat. No. 4,412,989), ribonuclease and superoxide dismutase(Veronese at al., App. Biochem. Biotech. 11: 141-45 (1985)).

PEGylation (i.e., addition of any water soluble polymer) of fEPOpolypeptides containing a non-naturally encoded amino acid, such asp-azido-L-phenylalanine, is carried out by any convenient method. Forexample, fEPO polypeptide is PEGylated with an alkyne-terminated mPEGderivative. Briefly, an excess of solid mPEG(5000)-O—CH₂—C≡CH is added,with stirring, to an aqueous solution of p-azido-L-Phe-containing fEPOat room temperature. Typically, the aqueous solution is buffered with abuffer having a pK_(a) near the pH at which the reaction is to becarried out {generally about pH 4-10). Examples of suitable buffers forPEGylation at pH 7.5, for instance, include, but are not limited to,HEPES, phosphate, borate, TRIS-HCl, EPPS, and TES. The pH iscontinuously monitored and adjusted if necessary. The reaction istypically allowed to continue for between about 1-48 hours.

The reaction products are subsequently subjected to hydrophobicinteraction chromatography to separate the PEGylated fEPO variants fromfree mPEG(5000)-O—CH₂—C≡CH and any high-molecular weight complexes ofthe pegylated fEPO polypeptide which may form when unblocked PEG isactivated at both ends of the molecule, thereby crosslinking fEPOvariant molecules. The conditions during hydrophobic interactionchromatography are such that free mPEG(5000)-O—CH₂—C≡CH flows throughthe column, while any crosslinked PEGylated fEPO variant complexes eluteafter the desired forms, which contain one fEPO variant moleculeconjugated to one or more PEG groups. Suitable conditions vary dependingon the relative sizes of the cross-linked complexes versus the desiredconjugates and are readily determined by those skilled in the art. Theeluent containing the desired conjugates is concentrated byultrafiltration and desalted by diafiltration.

If necessary, the PEGylated fEPO obtained from the hydrophobicchromatography can be purified further by one or more procedures knownto those skilled in the art including, but are not limited to, affinitychromatography; anion- or cation-exchange chromatography (using,including but not limited to, DEAE SEPHAROSE); chromatography on silica;reverse phase HPLC; gel filtration (using, including but not limited to,SEPHADEX G-75); hydrophobic interaction chromatography; size-exclusionchromatography, metal-chelate chromatography;ultrafiltration/diafiltration; ethanol precipitation; ammonium sulfateprecipitation; chromatofocusing; displacement chromatography;electrophoretic procedures (including but not limited to preparativeisoelec- tric focusing), differential solubility (including but notlimited to ammonium sulfate precipitation), or extraction. Apparentmolecular weight may be estimated by GPC by comparison to globularprotein standards (PROTEIN PURIFICATION METHODS, A PRACTICAL APPROACH(Harris & Angal, Eds.) IRL Press 1989, 293-306). The purity of thefEPO-PEG conjugate can be assessed by proteolytic degradation (includingbut not limited to, trypsin cleavage) followed by mass spectrometryanalysis. Pepinsky B., et al., J. Pharmcol. & Exp. Ther. 297(3):1059-66(2001).

A water soluble polymer linked to an amino acid of a fEPO polypeptide ofthe invention can be further derivatized or substituted withoutlimitation.

Azide-Containing PEG Derivatives

In another embodiment of the invention, a fEPO polypeptide is modifiedwith a PEG derivative that contains an azide moiety that will react withan alkyne moiety present on the side chain of the non-naturally encodedamino acid. In general, the PEG derivatives will have an averagemolecular weight ranging from 1-100 kDa and, in some embodiments, from10-40 kDa.

In some embodiments, the azide-tewiinal PEG derivative will have thestructure:

RO—(CH₂CH₂O)_(n)—O—(CH₂)_(m)—N₃

where R is a simple alkyl (methyl, ethyl, propyl, etc.), m is 2-10 and nis 100-1,000 (i.e., average molecular weight is between 5-40 kDa).

In another embodiment, the azide-terminal PEG derivative will have thestructure:

RO—(CH₂CH₂O)_(n)—O—(CH₂)_(m)—NH—C(O)—(CH₂)_(p)—N₃

where R is a simple alkyl (methyl, ethyl, propyl, etc.), m is 2-10, p is2-10 and n is 100-1,000 (i.e., average molecular weight is between 5-40kDa).

In another embodiment of the invention, a fEPO polypeptide comprising aalkyne-containing amino acid is modified with a branched PEG derivativethat contains a terminal azide moiety, with each chain of the branchedPEG having a MW ranging from 10-40 kDa and, more preferably, from 5-20kDa. For instance, in some embodiments, the azide-terminal PEGderivative will have the following structure:

[RO—(CH₂CH₂O)_(n)—O—(CH₂)₂—NH—C(O)]₂CH(CH₂)_(m)—X—(CH₂)_(p)N₃

where R is a simple alkyl (methyl, ethyl, propyl, etc.), m is 2-10, p is2-10, and n is 100-1,000, and X is optionally an O, N, S or carbonylgroup (C═O), in each case that can be present or absent.

Alkyne-Containing PEG Derivatives

In another embodiment of the invention, a fEPO polypeptide is modifiedwith a PEG derivative that contains an alkyne moiety that will reactwith an azide moiety present on the side chain of the non-naturallyencoded amino acid.

In some embodiments, the alkyne-terminal PEG derivative will have thefollowing structure:

RO—(CH₂CH₂O)_(n)—O—(CH₂)_(m)—C≡CH

where R is a simple alkyl (methyl, ethyl, propyl, etc.), m is 2-10 and nis 100-1,000 (i.e., average molecular weight is between 5-40 kDa).

In another embodiment of the invention, a fEPO polypeptide comprising analkyne-containing non-naturally encoded amino acid is modified with aPEG derivative that contains a terminal azide or terminal alkyne moietythat is linked to the PEG backbone by means of an amide linkage.

In some embodiments, the alkyne-terminal PEG derivative will have thefollowing structure:

RO—(CH₂CH₂O)_(n)—O—(CH₂)_(m)—NH—C(O)—(CH₂)_(p)—C≡CH

where R is a simple alkyl (methyl, ethyl, propyl, etc.), m is 2-10, p is2-10 and n is 100-1,000.

In another embodiment of the invention, a fEPO polypeptide comprising anazide-containing amino acid is modified with a branched PEG derivativethat contains a terminal alkyne moiety, with each chain of the branchedPEG having a MW ranging from 10-40 kDa and, more preferably, from 5-20kDa. For instance, in some embodiments, the alkyne-terminal PEGderivative will have the following structure:

[RO—(CH₂CH₂O)_(n)—O—(CH₂)₂—NH—C(O)]₂CH(CH₂)_(m)—X—(CH₂)_(p)C≡CH

where R is a simple alkyl (methyl, ethyl, propyl, etc.), m is 2-10, p is2-10, and n is 100-1,000, and X is optionally an O, N, S or carbonylgroup (C═O), or not present.

Phosphine-Containing PEG Derivatives

In another embodiment of the invention, a fEPO polypeptide is modifiedwith a PEG derivative that contains an activated functional group(including but not limited to, ester, carbonate) further comprising anaryl phosphine group that will react with an azide moiety present on theside chain of the non-naturally encoded amino acid. In general, the PEGderivatives will have an average molecular weight ranging from 1-100 kDaand, in some embodiments, from 10-40 kDa.

In some embodiments, the PEG derivative will have the structure:

wherein n is 1-10; X can be O, N, S or not present, Ph is phenyl, and Wis a water soluble polymer.

In some embodiments, the PEG derivative will have the structure:

wherein X can be O, N, S or not present, Ph is phenyl, W is a watersoluble polymer and R can be H, alkyl, aryl, substituted alkyl andsubstituted aryl groups. Exemplary R groups include but are not limitedto —CH₂, —C(CH₃)₃, —OR′, —NR′R″, —SR′, -halogen, —C(O)R′, —CONR′R″,—S(O)₂R′, —S(O)₂NR′R″, —CN and —NO₂. R′, R″, R′″ and R″″ eachindependently refer to hydrogen, substituted or unsubstitutedheteroalkyl, substituted or unsubstituted aryl, including but notlimited to, aryl substituted with 1-3 halogens, substituted orunsubstituted alkyl, alkoxy or thioalkoxy groups, or arylalkyl groups.When a compound of the invention includes more than one R group, forexample, each of the R groups is independently selected as are each R′,R″, R′″ and R″″ groups when more than one of these groups is present.When R′ and R″ are attached to the same nitrogen atom, they can becombined with the nitrogen atom to form a 5-, 6-, or 7-membered ring.For example, —NR′R″ is meant to include, but not be limited to,1-pyrrolidinyl and 4-morpholinyl. From the above discussion ofsubstituents, one of skill in the art will understand that the term“alkyl” is meant to include groups including carbon atoms bound togroups other than hydrogen groups, such as haloalkyl (including but notlimited to, —CF₃ and —CH₂CF₃) and acyl (including but not limited to,—C(O)CH₃, —C(O)CF₃, —C(O)CH₂OCH₃, and the like).

Other PEG Derivatives and General PEGvlation Techniques

Other exemplary PEG molecules that may be linked to fEPO polypeptides,as well as PEGylation methods include those described in, e.g., U.S.Patent Publication No. 2004/0001838; 2002/0052009; 2003/0162949;2004/0013637; 2003/0228274; 2003/0220447; 2003/0158333; 2003/0143596;2003/0114647; 2003/0105275; 2003/0105224; 2003/0023023; 2002/0156047;2002/0099133; 2002/0086939; 2002/0082345; 2002/0072573; 2002/0052430;2002/0040076; 2002/0037949; 2002/0002250; 2001/0056171; 2001/0044526;2001/0027217; 2001/0021763; U.S. Pat. Nos. 6,646,110; 5,824,778;5,476,653; 5,219,564; 5,629,384; 5,736,625; 4,902,502; 5,281,698;5,122,614; 5,473,034; 5,516,673; 5,382,657; 6,552,167; 6,610,281;6,515,100; 6,461,603; 6,436,386; 6,214,966; 5,990,237; 5,900,461;5,739,208; 5,672,662; 5,446,090; 5,808,096; 5,612,460; 5,324,844;5,252,714; 6,420,339; 6,201,072; 6,451,346; 6,306,821; 5,559,213;5,612,460; 5,747,646; 5,834,594; 5,849,860; 5,980,948; 6,004,573;6,129,912; WO 97/32607, EP 229,108, EP 402,378, WO 92/16555, WO94/04193, WO 94/14758, WO 94/17039, WO 94/18247, WO 94/28024, WO95/00162, WO 95/11924, WO95/13090, WO 95/33490, WO 96/00080, WO97/18832, WO 98/41562, WO 98/48837, WO 99/32134, WO 99/32139, WO99/32140, WO 96/40791, WO 98/32466, WO 95/06058, EP 439 508, WO97/03106, WO 96/21469, WO 95/13312, EP 921 131, WO 98/05363, EP 809 996,WO 96/41813, WO 96/07670, EP 605 963, EP 510 356, EP 400 472, EP 183 503and EP 154 316, which are incorporated by reference herein. Any of thePEG molecules described herein may be used in any form, including butnot limited to, single chain, branched chain, multiarm chain, singlefunctional, bi-functional, multi-functional, or any combination thereof.

Enhancing Affinity for Serum Albumin

Various molecules can also be fused to the fEPO polypeptides of theinvention to modulate the half-life of fEPO in serum. In someembodiments, molecules are linked or fused to fEPO polypeptides of theinvention to enhance affinity for endogenous serum albumin in an animal.

For example, in some cases, a recombinant fusion of a fEPO polypeptideand an albumin binding sequence is made. Exemplary albumin bindingsequences include, but are not limited to, the albumin binding domainfrom streptococcal protein G (see. e.g., Makrides et al., J. Pharmacol.Exp. Ther. 277:534-542 (1996) and Sjolander et al., J. Immunol. Methods201:115-123 (1997)), or albumin-binding peptides such as those describedin, e.g., Dennis, et al., J. Biol. Chem. 277:35035-35043 (2002).

In other embodiments, the fEPO polypeptides of the present invention areacylated with fatty acids. In some cases, the fatty acids promotebinding to serum albumin See, e.g., Kurtzhals, et al., Biochem. J.312:725-731 (1995).

In other embodiments, the fEPO polypeptides of the invention are fuseddirectly with serum albumin (including but not limited to, human serumalbumin). See, e.g., U.S. Pat. No. 6,548,653 which is incorporated byreference herein.

Those of skill in the art will recognize that a wide variety of othermolecules can also be linked to fEPO in the present invention tomodulate binding to serum albumin or other serum components.

XI. Glycosylation of fEPO

The invention includes fEPO polypeptides incorporating one or morenon-naturally encoded amino acids bearing saccharide residues. Thesaccharide residues may be either natural (including but not limited to,N-acetylglucosamine) or non-natural (including but not limited to,3-fluorogalactose). The saccharides may be linked to the non-naturallyencoded amino acids either by an N- or O-linked glycosidic linkage(including but not limited to, N-acetylgalactose-L-serine) or anon-natural linkage (including but not limited to, an oxime or thecorresponding C- or S-linked glycoside).

The saccharide (including but not limited to, glycosyl) moieties can beadded to fEPO polypeptides either in vivo or in vitro. In someembodiments of the invention, a fEPO polypeptide comprising acarbonyl-containing non-naturally encoded amino acid is modified with asaccharide derivatized with an aminooxy group to generate thecorresponding glycosylated polypeptide linked via an oxime linkage. Onceattached to the non-naturally encoded amino acid, the saccharide may befurther elaborated by treatment with glycosyltransferases and otherenzymes to generate an oligosaccharide bound to the fEPO polypeptide.See, e.g., H. Liu, et al. J. Am. Chem. Soc. 125: 1702-1703 (2003).

In some embodiments of the invention, a fEPO polypeptide comprising acarbonyl-containing non-naturally encoded amino acid is modifieddirectly with a glycan with defined structure prepared as an aminooxyderivative. One skilled in the art will recognize that otherfunctionalities, including azide, alkyne, hydrazide, hydrazine, andsemicarbazide, can be used to link the saccharide to the non-naturallyencoded amino acid.

In some embodiments of the invention, a fEPO polypeptide comprising anazide or alkynyl-containing non-naturally encoded amino acid can then bemodified by, including but not limited to, a Huisgen [3+2] cycloadditionreaction with, including but not limited to, alkynyl or azidederivatives, respectively. This method allows for proteins to bemodified with extremely high selectivity.

XII. GH Supergene Family Member Dimers and Multimers

The present invention also provides for GH supergene family membercombinations (including but not limited to fEPO) homodimers,heterodimers, homomultimers, or heteromultimers (i.e., trimers,tetramers, etc.) where a GH supergene family member polypeptide such asfEPO containing one or more non-naturally encoded amino acids is boundto another GH supergene family member or variant thereof or any otherpolypeptide that is a non-GH supergene family member or valiant thereof,either directly to the polypeptide backbone or via a linker. Due to itsincreased molecular weight compared to monomers, the GH supergene familymember, such as fEPO, dimer or multimer conjugates may exhibit new ordesirable properties, including but not limited to differentpharmacological, pharmacokinetic, pharmacodynamic, modulated therapeutichalf-life, or modulated plasma half-life relative to the monomeric GHsupergene family member. In some embodiments, the GH supergene familymember, such as fEPO, dimers of the invention will modulate thedimerization of the GH supergene family member receptor. In otherembodiments, the GH supergene family member dimers or multimers of thepresent invention will act as a GH supergene family member receptorantagonist, agonist, or modulator.

In some embodiments, one or more of the fEPO molecules present in a fEPOcontaining dimer or multimer comprises a non-naturally encoded aminoacid linked to a water soluble polymer that is present within the SiteII binding region. As such, each of the fEPO molecules of the dimer ormultimer are accessible for binding to the fEPO receptor via the Siteinterface but are unavailable for binding to a second fEPO receptor viathe Site II interface. Thus, the fEPO dimer or multimer can engage theSite I binding sites of each of two distinct fEPO receptors but, as thefEPO molecules have a water soluble polymer attached to anon-genetically encoded amino acid present in the Site II region, thefEPO receptors cannot engage the Site II region of the fEPO ligand andthe dimer or multimer acts as a fEPO antagonist. In some embodiments,one or more of the fEPO molecules present in a fEPO containing dimer ormultimer comprises a non-naturally encoded amino acid linked to a watersoluble polymer that is present within the Site I binding region,allowing binding to the Site II region. Alternatively, in someembodiments one or more of the fEPO molecules present in a fEPOcontaining dimer or multimer comprises a non-naturally encoded aminoacid linked to a water soluble polymer that is present at a site that isnot within the Site I or Site II binding region, such that both areavailable for binding. In some embodiments a combination of fEPOmolecules is used having Site I, Site II, or both available for binding.A combination of fEPO molecules wherein at least one has Site Iavailable for binding, and at least one has Site II available forbinding may provide molecules having a desired activity or property. Inaddition, a combination of fEPO molecules having both Site I and Site IIavailable for binding may produce a super-agonist fEPO molecule.

In some embodiments, the GH supergene family member polypeptides arelinked directly, including but not limited to, via an Asn-Lys amidelinkage or Cys-Cys disulfide linkage. In some embodiments, the linked GHsupergene family member polypeptides, and/or the linked non-GH supergenefamily member, will comprise different non-naturally encoded amino acidsto facilitate dimerization, including but not limited to, an alkyne inone non-naturally encoded amino acid of a first fEPO polypeptide and anazide in a second non-naturally encoded amino acid of a second GHsupergene family member polypeptide will be conjugated via a Huisgen[3+2] cycloaddition. Alternatively, a first GH supergene family member,and/or the linked non-GH supergene family member, polypeptide comprisinga ketone-containing non-naturally encoded amino acid can be conjugatedto a second GH supergene family member polypeptide comprising ahydroxylamine-containing non-naturally encoded amino acid and thepolypeptides are reacted via formation of the corresponding oxime.

Alternatively, the two GH supergene family member polypeptides, and/orthe linked non-GH supergene family member, are linked via a linker. Anyhetero- or homo-bifunctional linker can be used to link the two GHsupergene family member, and/or the linked non-GH supergene familymember, polypeptides, which can have the same or different primarysequence. In some cases, the linker used to tether the GH supergenefamily member, and/or the linked non-GH supergene family member,polypeptides together can be a bifunctional PEG reagent.

In some embodiments, the invention provides water-soluble bifunctionallinkers that have a dumbbell structure that includes: a) an azide, analkyne, a hydrazine, a hydrazide, hydroxylamine, or acarbonyl-containing moiety on at least a first end of a polymerbackbone; and b) at least a second functional group on a second end ofthe polymer backbone. The second functional group can be the same ordifferent as the first functional group. The second functional group, insome embodiments, is not reactive with the first functional group. Theinvention provides, in some embodiments, water-soluble compounds thatcomprise at least one arm of a branched molecular structure. Forexample, the branched molecular structure can be dendritic.

In some embodiments, the invention provides multimers comprising one ormore GH supergene family member, such as fEPO, formed by reactions withwater soluble activated polymers that have the structure:

R—(CH₂CH₂O)_(n)—O—(CH₂)_(m)—X

wherein n is from about 5 to 3,000, m is 2-10, X can be an azide, analkyne, a hydrazine, a hydrazide, an aminooxy group, a hydroxylamine, aacetyl, or carbonyl-containing moiety, and R is a capping group, afunctional group, or a leaving group that can be the same or differentas X. R can be, for example, a functional group selected from the groupconsisting of hydroxyl, protected hydroxyl, alkoxyl,N-hydroxysuccinimidyl ester, 1-benzotriazoly1 ester,N-hydroxysuccinimidyl carbonate, 1-benzotriazolyl carbonate, acetal,aldehyde, aldehyde hydrates, alkenyl, acrylate, methacrylate,acrylamide, active sulfone, amine, aminooxy, protected amine, hydrazide,protected hydrazide, protected thiol, carboxylic acid, protectedcarboxylic acid, isocyanate, isothiocyanate, maleimide, vinylsulfone,dithiopyridine, vinylpyridine, iodoacetamide, epoxide, glyoxals, diones,mesylates, tosylates, and Cresylate, alkene, and ketone.

XIII. Measurement of fEPO Activity and Affinity of fEPO for the fEPOReceptor

The fEPO receptor can be prepared as described in U.S. Pat. Nos.5,387,808; 5,292,654; 5,278,065, which are incorporated by referenceherein. fEPO polypeptide activity can be determined using standard invitro or in vivo assays. For example, cell lines that proliferate in thepresence of fEPO (including but not limited to, UT-7 cells, TF-1 cells,FDCP-1/mEPOR, or spleen cells) can be used to monitor fEPO receptorbinding. See, e.g., Wrighton et al., (1997) Nature Biotechnology15:1261-1265; U.S. Pat. Nos. 5,773,569; and 5,830,851, which areincorporated by rererence herein. For a non-PEGylated or PEGylated fEPOpolypeptide comprising a non-natural amino acid, the affinity of thehormone for its receptor can be measured by using a BIAcore™ biosensor(Pharmacia). In vivo animal models (e.g. murine, etc.) as well as felinetrials for testing fEPO activity are known and include those describedin, e.g., U.S. Pat. No. 6,696,056; Cotes et al., (1961) Nature191:1065-1067; U.S.Patent Application Pub. No. 2003/0198691; and PharmEuropa Spec. Issue Erythropoietin BRP Bio 1997(2), which areincorporated by reference herein. Assays for dimerization capability offEPO polypeptides comprising one or more non-naturally encoded aminoacids can be conducted as described in U.S. Pat. No. 6,221,608 which isincorporated by reference herein.

XIV. Measurement of Potency, Functional In Vivo Half-Life, andPharmacokinetic Parameters

The potency and functional in vivo half-life of a fEPO polypeptidecomprising a non-naturally encoded amino acid can be determinedaccording to the protocol described in U.S. Pat. Nos. 6,586,398;5,583,272; and U.S.Patent application Publication No. 2003/0198691A1,which are incorporated by reference herein.

Pharmacokinetic parameters for a fEPO polypeptide comprising anon-naturally encoded amino acid can be evaluated in normalSprague-Dawley male rats (N=5 animals per treatment group). Animals willreceive either a single dose of 25 ug/rat iv or 50 ug/rat so, andapproximately 5-7 blood samples will be taken according to a predefinedtime course, generally covering about 6 hours for a fEPO polypeptidecomprising a non-naturally encoded amino acid not conjugated to a watersoluble polymer and about 4 days for a fEPO polypeptide comprising anon-naturally encoded amino acid and conjugated to a water solublepolymer. Pharmacokinetic data for fEPO is well-studied in severalspecies and can be compared directly to the data obtained for fEPOcomprising a non-naturally encoded amino acid. See Mordenti S., et al.,Pharm. Res. 8(11):1351-59 (1991).

The specific activity of fEPO in accordance with this invention can bedetermined by various assays known in the art. The biological activityof the purified fEPO proteins of this invention are such thatadministration of the fEPO protein by injection to human patientsresults in bone marrow cells increasing production of reticulocytes andred blood cells compared to non-injected or control groups of subjects.The biological activity of the fEPO muteins, or fragments thereof,obtained and purified in accordance with this invention can be tested bymethods according to Pharm. Europa Spec. Issue Erythropoietin BRP Bio1997(2). Another biological assay for determining the activity of fEPOis the normocythaemic mouse assay (Pharm. Europa Spec. IssueErythropoietin BRP Bio 1997(2)).

XV. Administration and Pharmaceutical Compositions

The polypeptides or proteins of the invention (including but not limitedto, fEPO, synthetases, proteins comprising one or more unnatural aminoacid, etc.) are optionally employed for therapeutic uses, including butnot limited to, in combination with a suitable pharmaceutical carrier.Such compositions, for example, comprise a therapeutically effectiveamount of the compound, and a pharmaceutically acceptable carrier orexcipient. Such a carrier or excipient includes, but is not limited to,saline, buffered saline, dextrose, water, glycerol, ethanol, and/orcombinations thereof The formulation is made to suit the mode ofadministration. In general, methods of administering proteins are wellknown in the art and can be applied to administration of thepolypeptides of the invention.

Therapeutic compositions comprising one or more polypeptide of theinvention are optionally tested in one or more appropriate in vitroand/or in vivo animal models of disease, to confirm efficacy, tissuemetabolism, and to estimate dosages, according to methods well known inthe art. In particular, dosages can be initially determined by activity,stability or other suitable measures of unnatural herein to naturalamino acid homologues (including but not limited to, comparison of anEPO modified to include one or more unnatural amino acids to a naturalamino acid EPO), i.e., in a relevant assay.

Administration is by any of the routes normally used for introducing amolecule into ultimate contact with blood or tissue cells. The unnaturalamino acid containing polypeptides of the invention are administered inany suitable manner, optionally with one or more pharmaceuticallyacceptable carriers. Suitable methods of administering such polypeptidesin the context of the present invention to a patient are available, and,although more than one route can be used to administer a particularcomposition, a particular route can often provide a more immediate andmore effective action or reaction than another route.

Pharmaceutically acceptable carriers are determined in part by theparticular composition being administered, as well as by the particularmethod used to administer the composition. Accordingly, there is a widevariety of suitable formulations of pharmaceutical compositions of thepresent invention.

Polypeptide compositions can be administered by a number of routesincluding, but not limited to oral, intravenous, intraperitoneal,intramuscular, transdermal, subcutaneous, topical, sublingual, or rectalmeans. Unnatural amino acid polypeptide compositions can also beadministered via liposomes. Such administration routes and appropriateformulations are generally known to those of skill in the art.

The unnatural amino acid polypeptide, alone or in combination with othersuitable components, can also be made into aerosol formulations (i.e.,they can be “nebulized”) to be administered via inhalation. Aerosolformulations can be placed into pressurized acceptable propellants, suchas dichlorodifluoromethane, propane, nitrogen, and the like.

Formulations suitable for parenteral administration, such as, forexample, by intraarticular (in the joints), intravenous, intramuscular,intradellnal, intraperitoneal, and subcutaneous routes, include aqueousand non-aqueous, isotonic sterile injection solutions, which can containantioxidants, buffers, bacteriostats, and solutes that render theformulation isotonic with the blood of the intended recipient, andaqueous and non-aqueous sterile suspensions that can include suspendingagents, solubilizers, thickening agents, stabilizers, and preservatives.The formulations of packaged nucleic acid can be presented in unit-doseor multi-dose sealed containers, such as ampules and vials.

Parenteral administration and intravenous administration are preferredmethods of administration. In particular, the routes of administrationalready in use for natural amino acid homologue therapeutics (includingbut not limited to, those typically used for EPO, GCSF, GMCSF, IFNs,interleukins, antibodies, and/or any other pharmaceutically deliveredprotein), along with formulations in current use, provide preferredroutes of administration and formulation for the unnatural amino acidsof the invention.

The dose administered to a patient, in the context of the presentinvention, is sufficient to have a beneficial therapeutic response inthe patient over time, or, including but not limited to, to inhibitinfection by a pathogen, or other appropriate activity, depending on theapplication. The dose is determined by the efficacy of the particularvector, or formulation, and the activity, stability or serum half-lifeof the unnatural amino acid polypeptide employed and the condition ofthe patient, as well as the body weight or surface area of the patientto be treated. The size of the dose is also determined by the existence,nature, and extent of any adverse side-effects that accompany theadministration of a particular vector, formulation, or the like in aparticular patient.

In determining the effective amount of the vector or formulation to beadministered in the treatment or prophylaxis of disease (including butnot limited to, cancers, inherited diseases, diabetes, AIDS, or thelike), the physician evaluates circulating plasma levels, formulationtoxicities, progression of the disease, and/or where relevant, theproduction of anti-unnatural amino acid polypeptide antibodies.

The dose administered, for example, to a 70 kilogram patient, istypically in the range equivalent to dosages of currently-usedtherapeutic proteins, adjusted for the altered activity or serumhalf-life of the relevant composition. The vectors of this invention cansupplement treatment conditions by any known conventional therapy,including antibody administration, vaccine administration,administration of cytotoxic agents, natural amino acid polypeptides,nucleic acids, nucleotide analogues, biologic response modifiers, andthe like.

For administration, formulations of the present invention areadministered at a rate determined by the LD-50 of the relevantformulation, and/or observation of any side-effects of the unnaturalamino acids at various concentrations, including but not limited to, asapplied to the mass and overall health of the patient. Administrationcan be accomplished via single or divided doses.

If a patient undergoing infusion of a formulation develops fevers,chills, or muscle aches, he/she receives the appropriate dose ofaspirin, ibuprofen, acetaminophen or other pain/fever controlling drug.Patients who experience reactions to the infusion such as fever, muscleaches, and chills are premedicated 30 minutes prior to the futureinfusions with either aspirin, acetaminophen, or, including but notlimited to, diphenhydramine. Meperidine is used for more severe chillsand muscle aches that do not quickly respond to antipyretics andantihistamines. Cell infusion is slowed or discontinued depending uponthe severity of the reaction.

Feline EPO polypeptides of the invention can be administered directly toa mammalian subject. Administration is by any of the routes normallyused for introducing fEPO to a subject. The fEPO polypeptidecompositions according to embodiments of the present invention includethose suitable for oral, rectal, topical, inhalation (including but notlimited to, via an aerosol), buccal (including but not limited to,sub-lingual), vaginal, parenteral (including but not limited to,subcutaneous, intramuscular, intradermal, intraarticular, intrapleural,intraperitoneal, inracerebral, intraarterial, or intravenous), topical(i.e., both skin and mucosal surfaces, including airway surfaces) andtransdermal administration, although the most suitable route in anygiven case will depend on the nature and severity of the condition beingtreated. Administration can be either local or systemic. Theformulations of compounds can be presented in unit-dose or multi-dosesealed containers, such as ampoules and vials. fEPO polypeptides of theinvention can be prepared in a mixture in a unit dosage injectable form(including but not limited to, solution, suspension, or emulsion) with apharmaceutically acceptable carrier. fEPO polypeptides of the inventioncan also be administered by continuous infusion (using, including butnot limited to, minipumps such as osmotic pumps), single bolus orslow-release depot formulations.

Formulations suitable for administration include aqueous and non-aqueoussolutions, isotonic sterile solutions, which can contain antioxidants,buffers, bacteriostats, and solutes that render the formulationisotonic, and aqueous and non-aqueous sterile suspensions that caninclude suspending agents, solubilizers, thickening agents, stabilizers,and preservatives. Solutions and suspensions can be prepared fromsterile powders, granules, and tablets of the kind previously described.

The pharmaceutical compositions of the invention may comprise apharmaceutically acceptable carrier. Pharmaceutically acceptablecarriers are determined in part by the particular composition beingadministered, as well as by the particular method used to administer thecomposition. Accordingly, there is a wide variety of suitableformulations of pharmaceutical compositions (including optionalpharmaceutically acceptable carriers, excipients, or stabilizers) of thepresent invention (see, e.g., Remington's Pharmaceutical Sciences,17^(th) ed. 1985)).

Suitable carriers include buffers containing phosphate, borate, HEPES,citrate, and other organic acids; antioxidants including ascorbic acid;low molecular weight (less than about 10 residues) polypeptides;proteins, such as serum albumin, gelatin, or immunoglobulins;hydrophilic polymers such as polyvinylpyrrolidone; amino acids such asglycine, glutamine, asparagine, arginine, or lysine; monosaccharides,disaccharides, and other carbohydrates, including glucose, mannose, ordextrins; chelating agents such as EDTA; divalent metal ions such aszinc, cobalt, or copper; sugar alcohols such as mannitol or sorbitol;salt-forming counter ions such as sodium; and/or nonionic surfactantssuch as Tween™, Pluronics™, or PEG.

fEPO polypeptides of the invention, including those linked to watersoluble polymers such as PEG can also be administered by or as part ofsustained-release systems. Sustained-release compositions include,including but not limited to, semi-pelineable polymer matrices in theform of shaped articles, including but not limited to, films, ormicrocapsules. Sustained-release matrices include from biocompatiblematerials such as poly(2-hydroxyethyl methacrylate) (Langer et al., J.Biomed. Mater. Res., 15: 167-277 (1981); Langer, Chem. Tech., 12: 98-105(1982), ethylene vinyl acetate (Langer et al., supra) orpoly-D-(−)-3-hydroxybutyric acid (EP 133,988), polylactides (polylacticacid) (U.S. Pat. No. 3,773,919; EP 58,481), polyglycolide (polymer ofglycolic acid), polylactide co-glycolide (copolymers of lactic acid andglycolic acid) polyanhydrides, copolymers of L-glutamic acid andgamma-ethyl-L-glutamate (U. Sidman et al., Biopolymers, 22, 547-556(1983), poly(ortho)esters, polypeptides, hyaluronic acid, collagen,chondroitin sulfate, carboxylic acids, fatty acids, phospholipids,polysaccharides, nucleic acids, polyamino acids, amino acids such asphenylalanine, tyrosine, isoleucine, polynucleotides, polyvinylpropylene, polyvinylpyrrolidone and silicone. Sustained-releasecompositions also include a liposomally entrapped compound. Liposomescontaining the compound are prepared by methods known per se: DE3,218,121; Epstein et al. Proc. Natl. Acad. Sci. U.S.A., 82: 3688-3692(1985); Hwang et al., Proc. Natl. Acad. Sci. USA., 77: 4030-4034 (1980);EP 52,322; EP 36,676; EP 88,046; EP 143,949; EP 142,641; Japanese Pat.Appln. 83-118008; U.S. Pat. Nos. 4,485,045 and 4,544,545; and EP102,324.

Liposomally entrapped fEPO polypeptides can be prepared by methodsdescribed in, e.g., DE 3,218,121; Epstein et al., Proc. Natl. Acad. Sci.U.S.A., 82: 3688-3692 (1985); Hwang et al., Proc. Natl. Acad. Sci.U.S.A., 77: 4030-4034 (1980); EP 52,322; EP 36,676; EP 88,046; EP143,949; EP 142,641; Japanese Pat. Appln. 83-118008; U.S. Pat. Nos.4,485,045 and 4,544,545; and EP 102,324. Composition and size ofliposomes are well known or able to be readily determined empirically byone skilled in the art. Some examples of liposomes asdescribed in, e.g.,Park J W, et al., Proc. Natl. Acad. Sci. USA 92:1327-1331 (1995); LasicD and Papahadjopoulos D (eds): MEDICAL APPLICATIONS OF LIPOSOMES (1998);Drummond D C, et al., Liposomal drug delivery systems for cancertherapy, in Teicher B (ed): CANCER DRUG DISCOVERY AND DEVELOPMENT(2002); Park J W, et al., Clin. Cancer Res. 8:1172-1181 (2002); NielsenU B, et al., Biochim. Biophys. Acta 1591(1-3):109-118 (2002); Mamot C,et al., Cancer Res. 63: 3154-3161 (2003).

The dose administered to a patient in the context of the presentinvention should be sufficient to cause a beneficial response in thesubject over time. Generally, the total pharmaceutically effectiveamount of the fEPO of the present invention administered parenterallyper dose is in the range of about 0.01 μg/kg/day to about 100 μg/kg, orabout 0.05 mg/kg to about 1 mg/kg, of patient body weight, although thisis subject to therapeutic discretion. The frequency of dosing is alsosubject to therapeutic discretion, and may be more frequent or lessfrequent than the commercially available EPO products approved for usein humans. Generally, a PEGylated fEPO polypeptide of the invention canbe administered by any of the routes of administration described above.

XVI. Therapeutic Uses of fEPO Polypeptides of the Invention

The fEPO polypeptides of the invention are useful for treating a widerange of disorders. Administration of the fEPO products of the presentinvention results in red blood cell formation in humans. Thepharmaceutical compositions containing the fEPO glycoprotein productsmay be formulated at a strength effective for administration by variousmeans to a human patient experiencing blood disorders, characterized bylow or defective red blood cell production, either alone or as partcondition or disease. Average quantities of the fEPO glycoproteinproduct may vary and in particular should be based upon therecommendations and prescription of a qualified physician. The exactamount of fEPO is a matter of preference subject to such factors as theexact type of condition being treated, the condition of the patientbeing treated, as well as the other ingredients in the composition. ThefEPO of the present invention may thus be used to stimulate red bloodcell production and correct depressed red cell levels. Most commonly,red cell levels are decreased due to anemia. Among the conditionstreatable by the present invention include anemia associated with adecline or loss of kidney function (chronic renal failure), anemiaassociated with myelosuppressive therapy, such as chemotherapeutic oranti-viral drugs (such as AZT), anemia associated with the progressionof non-myeloid cancers, and anemia associated with viral infections(such as HIV). Also treatable are conditions which may lead to anemia inan otherwise healthy individual, such as an anticipated loss of bloodduring surgery. In general, any condition treatable with fEPO may alsobe treated with the PEG:fEPO conjugates of the present invention. Theinvention also provides for administration of a therapeuticallyeffective amount of iron in order to maintain increased erythropoiesisduring therapy. The amount to be given may be readily determined by oneskilled in the art based upon therapy with fEPO.

XVII. Examples

The following examples are offered to illustrate, but not to limit theclaimed invention.

Example 1

This example describes one of the many potential sets of criteria forthe selection of preferred sites of incorporation of non-naturallyencoded amino acids into fEPO.

This example demonstrates how preferred sites within the fEPOpolypeptide were selected for introduction of a non-naturally encodedamino acid. Molecular modeling and known information regarding thesecondary structure of fEPO was used to determine preferred positionsinto which one or more non-naturally encoded amino acids could beintroduced. Other fEPO structures and known crystal structureinformation regarding fEPO was utilized to examine potential variationof primary, secondary, or tertiary structural elements between crystalstructure datasets. The coordinates for these structures are availablefrom the Protein Data Bank (PDB) (Bernstein et al. J. Mol. Biol. 1997,112, pp 535) or via The Research Collaboratory for StructuralBioinformatics PDB at http://www.rcsb.org. The structural model 1 CN4contains the entire mature 18 kDa sequence of fEPO with the exception ofresidues 124-130, the N-terminal A1, and the C-terminal T163, G164,D165, and R166 residues which were omitted due to disorder in thecrystal. Two disulfide bridges are present, formed by C7 and C161 andC29 and C33.

Sequence numbering used in this example is according to the amino acidsequence of mature fEPO (18 kDa variant) shown in SEQ ID NO: 2 and SEQID NO: 4.

This example describes one of the many potential sets of criteria forthe selection of preferred sites of incorporation of non-naturallyencoded amino acids into fEPO. Using the criteria described below, theamino acid positions utilized for site-specific incorporation ofnon-naturally encoded amino acids (for example, p-acetyl-phenylalanine(pAF)) are positions: 53, 55, 116, 89, 72, 86, 128, 129, 130, 131, 132,133, 134, 135, 31, 163, 120, 76, 24, 38, 37, 49, 83, 21, 36. Several EPOcrystal structures were used to determine preferred positions into whichone or more non-naturally encoded amino acids could be introduced: thecoordinates for these structures are available from the Protein DataBank (PDB) via The Research Collaboratory for Structural Bioinformaticsat www.rcsb.org (PDB IDs 1CN4, lEER, and 1BUY). X-ray crystal structureinformation was used to perform solvent accessibility calculations onthe fEPO molecule, utilizing the Cx program (Pintar et al.Bioinformatics, 2002, Vol. 18, p 980). The solvent accessibility of allatoms was calculated and an average Cx value for each amino acid residuewas determined, and is shown in FIG. 8 and FIG. 9. The followingcriteria were used to evaluate each position of fEPO for theintroduction of a non-naturally encoded amino acid: the residue (a)should not interfere with binding of either fEPObp based on structuralanalysis of fEPO and structural analysis of fEPO and 1CN4, 1EER, and1BUY (crystallographic structures of hEPO conjugated with hEPOpb), b)should not be affected by alanine scanning mutagenesis (Bittorf, T. etal. FEBS, 336:133-136 (1993), Wen, D., et al. JBC, 269:22839-22846(1994), and Elliot, S. et al. Blood, 89:493-502 (1997), (c) should besurface exposed and exhibit a maximum Cx, demonstrating minimal van derWaals or hydrogen bonding interactions with surrounding residues, (d)should be either deleted or variable in fEPO variants (Bittorf, T. etal. FEBS, 336:133-136 (1993), Wen, D., et al. JBC, 269:22839-22846(1994), (e) would result in conservative changes upon substitution witha non-naturally encoded amino acid and (f) could be found in eitherhighly flexible regions (including but not limited to CD loop) orstructurally rigid regions (including but not limited to Helix B). Inaddition, further calculations were performed on the fEPO molecule,utilizing the Cx program (Pintar et al. Bioinformatics, 18, pp 980) toevaluate the extent of protrusion for each protein atom. As a result, insome embodiments, the non-naturally encoded encoded amino acid issubstituted at, but not limited to, one or more of the followingpositions of fEPO: before position 1 (i.e., at the N-terminus), 1, 2, 3,4, 7 , 8, 9, 10, 13, 17, 20, 21, 24, 25, 27, 30, 31, 32, 34, 36, 37, 38,40, 43, 49, 50, 52, 53, 54, 55, 56, 58, 65, 68, 69, 72, 75, 76, 79, 80,82, 83, 84, 85, 86, 87, 88, 89, 90, 92, 93, 110, 111, 115, 116, 117,118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131,132, 133, 134, 136, 139, 159, 161, 162, 163, 164, 165, 166, 167 (i.e.,at the carboxyl terminus of the protein), or combinations thereof.

Some sites for generation of a fEPO antagonist include: 10, 11, 14, 15,96, 97, 100, 103, 104, 107, 110. These sites were chosen utilizingcriteria c-e of the agonist design. The antagonist design may alsoinclude site-directed modifications of site 1 residues to increasebinding affinity to fEPObp.

FIGS. 3-9 show modeling and selection of positions. FIG. 8 shows that insome embodiments, the non-naturally encoded encoded amino acid issubstituted at, but not limited to, one or more of the followingpositions of fEPO: 53, 55, 116, 89, 72, 86, 128, 129, 130, 131, 132,133, 134, 135, 31, 163, 120, or combinations thereof. FIG. 9 shows thatin some embodiments, the non-naturally encoded encoded amino acid issubstituted at, but not limited to, one or more of the followingpositions of fEPO: 53, 55, 76, 24, 116, 38, 89, 37, 72, 86, 49, 83, 21,36, 128, 129, 130, 131, 132, 133, or combinations thereof.

Example 2

This example details cloning and expression of a modified fEPOpolypeptide in E. coli.

This example demonstrates how a fEPO polypeptide including anon-naturally encoded amino acid can be expressed in E. coli. Nucleotidesequences encoding fEPO are produced generally as described in Matthewset al., (1996) PNAS 93:9471-76. Fetal liver, adult liver, fetal kidneyand adult kidney cDNA libraries are templates for cloning cDNA encodingfull length and mature fEPO, with fetal liver giving the best relult.Primers used for cloning full length and mature fEPO could be primersknown to those skilld in the art including5′cagttacatatgggagttcaegaatgtectgcctgg3′SEQIDNO: 21; and5′cagttacatatgetccaccaagattaatetgtg3′SEQIDNO: 22. An example of a 3′primer sequence that could be used for this cloning is5′etgeaactegagtcatctgtcceetgtcetgcag3′ SEQIDNO: 23. The reactionconditions for the cloning can be 94° C. for two minutes, with 30 cyclesof 94° C. for 30 seconds, 50° C. for one minute, 72° C. for 2 minutes,and 72° C. for 7 minutes, followed by 4° C. reaction termination.Molecules are identified that encode fEPO, including the full lengthfEPO, the mature form of fEPO lacking the N-terminal signal sequence,and SNPs. The full length and mature fEPO encoding cDNA can be insertedinto expression vectors, such as the pBAD HISc, and pET20b expressionvectors following optimization of the sequence for cloning andexpression without altering amino acid sequence.

An introduced translation system that comprises an orthogonal tRNA(O-tRNA) and an orthogonal aminoacyl tRNA synthetase (O-RS) is used toexpress fEPO containing a non-naturally encoded amino acid, The O-RSpreferentially aminoacylates the O-tRNA with a non-naturally encodedamino acid. In turn the translation system inserts the non-naturallyencoded amino acid into fEPO, in response to an encoded selector codon.The following Table (Table 2) includes sequences of fEPO, both fulllength and mature, and O-RS and O-tRNA sequences, some of which used inthese examples, others which were used with hEPO and may be used oroptimized for use with fEPO.

TABLE 2 SEQ ID # Sequence Notes Protein of tRNA or RS 1MGSCECPALLLLLSLLLLPLGLPVLGAPPRLICDSRVLERYILEAREAENVTM Full-length aminoacid sequence Protein GCAEGCSFSENITVPDTKVNFYTWKRMDVGQQAVEVWQGLALLSEAILRGof fEPO QALLANSSQPSETLQLHVDKAVSSLRSLTSLLRALGAQKEATSLPEATSAAPLRTFTVDTLCKLFRIYSNFLRGKLTLYTGEACRRGDR 2APPRLICDSRVLERYILEAREAENVTMGCAEGCSFSENITVPDTKVNFYTWK The mature aminoProtein RMDVGQQAVEVWQGLALLSEAILRGQALLANSSQPSETLQLHVDKAVSSLR acidsequence of fEPO SLTSLLRALGAQKEATSLPEATSAAPLRTFTVDTLCKLFRIYSNFLRGKLTLYTGEACRRGDR 3 MGSCECPALLLLLSLLLLPLGLPVLGAPPRLICDSRVLERYILGAREAENVTM SNPvariant (E108G) proteinGCAEGCSFSENITVPDTKVNFYTWKRMDVGQQAVEVWQGLALLSEAILRG of the full-lengthQALLANSSQPSETLQLHVDKAVSSLRSLTSLLRALGAQKEATSLPEATSAAP amino acid sequenceLRTFTVDTLCKLFRIYSNFLRGKLTLYTGEACRRGDR of fEPO 4APPRLICDSRVLERYILGAREAENVTMGCAEGCSFSENITVPDTKVNFYTWK SNP variant (E108G)protein RMDVGQQAVEVWQGLALLSEAILRGQALLANSSQPSETLQLHVDKAVSSLR of themature amino SLTSLLRALGAQKEATSLPEATSAAPLRTFTVDTLCKLFRIYSNFLRGKLTLY acidsequence of fEPO TGEACRRGDR 5CCCAGGGTAGCCAAGCTCGGCCAACGGCGACGGACTCTAAATCCGTTCT HLAD03; an tRNACGTAGGAGTTCGAGGGTTCGAATCCCTTCCC TGGGACCA optimized amber supressor tRNA6 GCGAGGGTAGCCAAGCTCGGCCAACGGCGACGGACTTCCTAATCCGTTC HL325A; an optimizedtRNA TCGTAGGAGTTCGAGGGTTCGAATCCCTCCCCTCGCACCA AGGA frameshift supressortRNA 7 MDEFEMIKRNTSEIISEEELREVLKKDEKSAGIGFEPSGKIHLGHYLQIKKMID AminoacyltRNA RS LQNAGFDIIILLADLHAYLNQKGELDEIRKIGDYNKKVFEAMGLKAKYVYGS synthetasefor the TFQLDKDYTLNVYRLALKTTLKRARRSMELIAREDENPKVAEVIYPIMQVNTincorporation of p- YYYLGVDVAVGGMEQRKIHMLARELLPKKVVCIHNPVLTGLDGEGKMSSSazido-L-phenylalanineKGNFIAVDDSPEEIRAKIKKAYCPAGVVEGNPIMEIAKYFLEYPLTIKRPEKF p-Az-PheRS(6)GGDLTVNSYEELESLFKNKELHPMDLKNAVAEELIKILEPIRKRL 8MDEFEMIKRNTSEIISEEELREVLKKDEKSAGIGFEPSGKIHLGHYLQIKKMID Aminoacyl tRNA RSLQNAGFDIIILLADLHAYLNQKGELDEIRKIGDYNKKVFEAMGLKAKYVYGS synthetase for theSFQLDKDYTLNVYRLALKTTLKRARRSMELIAREDENPKVAEVIYPIMQVNT incorporation of p-SHYLGVDVAVGGMEQRKIHMLARELLPKKVVCIHNPVLTGLDGEGKMSSS benzoyl-L-KGNFIAVDDSPEEIRAKIKKAYCPAGVVEGNPIMEIAKYFLEYPLTIKRPEKF phenylalanineGGDLTVNSYEELESLFKNKELHPMDLKNAVAEELIKILEPIRKRL p-BpaRS(1) 9MDEFEMIKRNTSEIISEEELREVLKKDEKAAIGFEPSGKIHLGHYLQIKKMIDL Aminoacyl tRNA RSQNAGFDIIILLADLHAYLNQKGELDEIRKIGDYNKKVFEAMGLKAKYVYGSP synthetase for theFQLDKDYTLNVYRLALKTTLKRARRSMELIAREDENPKVAEVIYPIMQVNAI incorporation ofYLAVDVAVGGMEQRKIHMLARELLPKKVVCIHNPVLTGLDGEGKMSSSKG propargyl-NFIAVDDSPEEIRAKIKKAYCPAGVVEGNPIMEIAKYFLEYPLTIKRPEKFGG phenylalanineDLTVNSYEELESLFKNKELHPMDLKNAVAEELIKILE PIRKR L Propargyl-PheRS 10 MDEFEMIKRN TSEII SEEEL REVLK KDEKS AAIGF EPSGK IHLGH YLQIK Aminoacyl tRNA RSKMIDL QNAGF DIIIL LADLH AYLNQ KGELD EIRKI GDYNK KVFEA synthetase for theMGLKA KYVYG SPFQL DKDYT LNVYR LALKT TLKRA RRSME LIARE incorporation ofDENPK VAEVI YPIMQ VNIPY LPVD VAVGG MEQRK IHMLA RELLP propargyl- KKVVCIHNPV LTGLD GEGKM SSSKG NFIAV DDSPE EIRAK IKKAY phenylalanine CPAGVVEGNP IMEIA KYFLE YPLTI KRPEK FGGDL TVNSY EELES Propargyl-PheRS LFKNKELHPM DLKNA VAEEL IKILE PIRKR L 11 MDEFE MIKRN TSEII SEEEL REVLK KDEKSAAIGF EPSGK IHLGH YLQIK Aminoacyl tRNA RS KMIDL QNAGF DIIIL LADLH AYLNQKGELD EIRKI GDYNK KVFEA synthetase for the MGLKA KYVYG SKFQL DKDYT LNVYRLALKT TLKRA RRSME LIARE incorporation of DENPK VAEVI YPIMQ VNAIY LAVDVAVGG MEQRK IHMLA RELLP propargyl- KKVVC IHNPV LTGLD GEGKM SSSKG NFIAVDDSPE EIRAK IKKAY phenylalanine CPAGV VEGNP IMEIA KYFLE YPLTI KRPEKFGGDL TVNSY EELES Propargyl-PheRS LFKNK ELHPM DLKNA VAEEL IKILE PIRKR L12 MDEFEMIKRNTSEIISEEELREVLKKDEKSATIGFEPSGKIHLGHYLQIKKMID Aminoacyl tRNARS LQNAGFDIIILLADLHAYLNQKGELDEIRKIGDYNKKVFEAMGLKAKYVYGS synthetase forthe NFQLDKDYTLNVYRLALKTTLKRARRSMELIAREDENPKVAEVIYPIMQVN incorporation ofp- PLHYQGVDVAVGGMEQRKIHMLARELLPKKVVCIHNPVLTGLDGEGKMSS azido-phenylalaineSKGNFIAVDDSPEEIRAKIKKAYCPAGVVEGNPIMEIAKYFLEYPLTIKRPEKF p-Az-PheRS(1)GGDLTVNSYEELESLFKNKELHPMDLKNAVAEELIKILEPIRKRL 13MDEFEMIKRNTSEIISEEELREVLKKDEKSATIGFEPSGKIHLGHYLQIKKMID Aminoacyl tRNA RSLQNAGFDIIILLADLHAYLNQKGELDEIRKIGDYNKKVFEAMGLKAKYVYGS synthetase for theSFQLDKDYTLNVYRLALKTTLKRARRSMELIAREDENPKVAEVIYPIMQVNP incorporation of p-LHYQGVDVAVGGMEQRKIHMLARELLPKKVVCIHNPVLTGLDGEGKMSSS azido-phenylalanineKGNFIAVDDSPEEIRAKIKKAYCPAGVVEGNPIMEIAKYFLEYPLTIKRPEKF p-Az-PheRS(3)GGDLTVNSYEELESLFKNKELHPMDLKNAVAEELIKILEPIRKRL 14MDEFEMIKRNTSEIISEEELREVLKKDEKSALIGFEPSGKIHLGHYLQIKKMID Aminoacyl tRNA RSLQNAGFDIIILLADLHAYLNQKGELDEIRKIGDYNKKVFEAMGLKAKYVYGS synthetase for theTFQLDKDYTLNVYRLALKTTLKRARRSMELIAREDENPKVAEVIYPIMQVNP incorporation of p-VHYQGVDVAVGGMEQRKIHMLARELLPKKVVCIHNPVLTGLDGEGKMSSS azido-phenylalanineKGNFIAVDDSPEEIRAKIKKAYCPAGVVEGNPIMEIAKYFLEYPLTIKRPEKF p-Az-PheRS(4)GGDLTVNSYEELESLFKNKELHPMDLKNAVAEELIKILEPIRIKRL 15MDEFEMIKRNTSEIISEEELREVLKKDEKSATIGFEPSGKIHLGHYLQIKKMID Aminoacyl tRNA RSLQNAGFDIIILLADLHAYLNQKGELDEIRKIGDYNKKVFEAMGLKAKYVYGS synthetase for theSFQLDKDYTLNVYRLALKTTLKRARRSMELIAREDENPKVAEVIYPIMQVNP incorporation of p-SHYQGVDVAVGGMEQRKIHMLARELLPKKVVCIHNPVLTGLDGEGKMSSS azido-phenylalanineKGNFIAVDDSPEEIRAKIKKAYCPAGVVEGNPIMEIAKYFLEYPLTIKRPEKF p-Az-PheRS(2)GGDLTVNSYEELESLFKNKELHPMDLKNAVAEELIKILEPIRKRL 16MDEFEMIKRNTSEIISEEELREVLKKDEKSALIGFEPSGKIHLGHYLQIKKMID Aminoacyl tRNA RSLQNAGFDIIILLADLHAYLNQKGELDEIRKIGDYNKKVFEAMGLKAKYVYGS synthetase for theEFQLDKDYTLNVYRLALKTTLKRARRSMELIAREDENPKVAEVIYPIMQVN incorporation of p-GCHYRGVDVAVGGMEQRKIHMLARELLPKKVVCIHNPVLTGLDGEGKMSS azido-phenylalanineSKGNFIAVDDSPEEIRAKIKKAYCPAGVVEGNPIMEIAKYFLEYPLTIKRPEKF (LW1)GGDLTVNSYEELESLFKNKELHPMDLKNAVAEELIKILEPIRKRL 17MDEFEMIKRNTSEIISEEELREVLKKDEKSALIGFEPSGKIHLGHYLQIKKMID Aminoacyl tRNA RSLQNAGFDIIILLADLHAYLNQKGELDEIRKIGDYNKKVFEAMGLKAKYVYGS synthetase for theEFQLDKDYTLNVYRLALKTTLKRARRSMELIAREDENPKVAEVIYPIMQVN incorporation of p-GTHYRGVDVAVGGMEQRKIHMLARELLPKKVVCIHNPVLTGLDGEGKMSS azido-phenylalanineSKGNFIAVDDSPEEIRAKIKKAYCPAGVVEGNPIMEIAKYFLEYPLTIKRPEKF (LW5)GGDLTVNSYEELESLFKNKELHPMDLKNAVAEELIKILEPIRKRL 18MDEFEMIKRNTSEIISEEELREVLKKDEKSAAIGFEPSGKIHLGHYLQIKKMID Aminoacyl tRNA RSLQNAGFDIIILLADLHAYLNQKGELDEIRKIGDYNKKVFEAMGLKAKYVYGS synthetase for theEFQLDKDYTLNVYRLALKTTLKRARRSMELIAREDENPKVAEVIYPIMQVN incorporation of p-GGHYLGVDVIVGGMEQRKIHMLARELLPKKVVCIHNPVLTGLDGEGKMSSS azido-phenylalanineKGNFIAVDDSPEEIRAKIKKAYCPAGVVEGNPIMEIAKYFLEYPLTIKRPEKF (LW6)GGDLTVNSYEELESLFKNKELHPMDLKNAVAEELIKILEPIRKRL 19MDEFEMIKRNTSEIISEEELREVLKKDEKSAAIGFEPSGKIHLGHYLQIKKMID Aminoacyl tRNA RSLQNAGFDIIILLADLHAYLNQKGELDEIRKIGDYNKKVFEAMGLKAKYVYGS synthetase for theRFQLDKDYTLNVYRLALKTTLKRARRSMELIAREDENPKVAEVIYPIMQVN incorporation of p-VIHYDGVDVAVGGMEQRKIHMLARELLPKKVVCIHNPVLTGLDGEGKMSS azido-phenylalanineSKGNFIAVDDSPEEIRAKIKKAYCPAGVVEGNPIMEIAKYFLEYPLTIKRPEKF (AzPheRS-5)GGDLTVNSYEELESLFKNKELHPMDLKNAVAEELIKILEPIRKRL 20MDEFEMIKRNTSEIISEEELREVLKKDEKSAGIGFEPSGKIHLGHYLQIKKMID Aminoacyl tRNA RSLQNAGFDIIILLADLHAYLNQKGELDEIRKIGDYNKKVFEAMGLKAKYVYGS synthetase for theTFQLDKDYTLNVYRLALKTTLKRARRSMELIAREDENPKVAEVIYPIMQVNT incorporation of p-YYYLGVDVAVGGMEQRKIHMLARELLPKKVVCIHNPVLTGLDGEGKMSSS azido-phenylalanineKGNFIAVDDSPEEIRAKIKKAYCPAGVVEGNPIMEIAKYFLEYPLTIKRPEKF (AzPheRS-6)GGDLTVNSYEELESLFKNKELHPMDLKNAVAEELIKILEPIRKRL 21cagttacatatgggagttcacgaatgtcctgcctgg Primer for cloning full length hEPOcDNA 22 cagttacatatgctccaccaagattaatctgtg Primer for cloning mature hEPOcDNA 23 ctgcaactcgagtcatctgtcccctgtcctgcag 3′Primer for cloning fulllength and mature hEPO cDNA 24atgggggtgcacgaatgtcctgcctggctgtggcttctcctgtccctgctgtcgctccctctgggcctcccagtcctgggcNucleotide sequencegccccaccacgcctcatctgtgacagccgagtcctggagaggtacctcttggaggccaaggaggccgagaatatcacgof full length hEPOacgggctgtgctgaacactgcagcttgaatgagaatatcactgtcccagacaccaaagttaatttctatgcctggaagaggcDNAatggaggtcgggcagcaggccgtagaagtctggcagggcctggccctgctgtcggaagctgtcctgcggggccaggccctgttggtcaactcttcccagccgtgggagcccctgcagctgcatgtggataaagccgtcagtggccttcgcagcctcaccactctgcttcgggctctgcgagcccagaaggaagccatctcccctccagatgcggcctcagctgctccactccgaacaatcactgctgacactttccgcaaactcttccgagtctactccaatttcctccggggaaagctgaagctgtacacaggggaggcctgcaggacaggggacagatga 25gccccaccacgcctcatctgtgacagccgagtcctggagaggtacctcttggaggccaaggaggccgagaatatcacgNucleotide sequenceacgggctgtgctgaacactgcagcttgaatgagaatatcactgtcccagacaccaaagttaatttctatgcctggaagaggof mature hEPOatggaggtcgggcagcaggccgtagaagtctggcagggcctggccctgctgtcggaagctgtcctgcggggccaggccDNAcctgttggtcaactcttcccagccgtgggagcccctgcagctgcatgtggataaagccgtcagtggccttcgcagcctcaccactctgcttcgggctctgcgagcccagaaggaagccatctcccctccagatgcggcctcagctgctccactccgaacaatcactgctgacactttccgcaaactcttccgagtctactccaatttcctccggggaaagctgaagctgtacacaggggaggcctgcaggacaggggacagatga 26gccccaccacgcctcatctgtgacagccgagtcctggagaggtacctcttggaggccaaggaggccgagaatatcacgNucleolide sequenceacgggctggctgaacactgcagcttgaatgagaatatcactgtcccagacaccaaagttaatttctatgcctggaagaggof G113R hEPOatggaggtcgggcagcaggccgtagaagtctggcagggcctggccctgctgtcggaagctgtcctgcggggccaggccDNAcctgttggtcaactcttcccagccgtgggagcccctgcagctgcatgtggataaagccgtcagtggccttcgcagcctcaccactctgcttcgggctctgggagcccagaaggaagccatctcccctccagatgcggcctcagctgctccactccgaacaatcactgctgacactttccgcaaactcttccgagtctactccaatttcctccggggaaagctgaagctgtacacaggggaggcctgcaggacaggggacagatga 27atgctccaccaagattaatctgtgacagccgagtcctggagaggtacctcttggaggccaaggaggccgagaatatcacOptimized forgacgggctgtgctgaacactgcagcttgaatgagaatatcactgtcccagacaccaaagttaatttctatgcctggaagagexpression of maturegatggaggtcgggcagcaggccgtagaagtctggcagggcctggccctgctgtcggaagctgtcctgcggggccagghEPO cDNA in E. coliccctgttggtcaactcttcccagccgtgggagcccctgcagctgcatgtggataaagccgtcagtggccttcgcagcctcaccactctgcttcgggctctgcgagcccagaaggaagccatctcccctccagatcggcggcctcagctgctccactccgaacaatcactgctgacactttccgcaaactcttccgagtctactccaatttcctccggggaaagctgaagctgtacacaggggaggcctgcaggacaggggacagatga 30MCEPAPPKPTQSAWHSFPECPALLLLLSLLLLPLGLPVLGAPPRLIC Full-length aminoProtein DSRVLERYILEAREAENVTMGCAQGCSFSENITVPDTKVNFYTWKR acid sequence ofMDVGQQALEVWQGLALLSEAILRGQALLANASQPSETPQLHVDKA cEPOVSSLRSLTSLLRALGAQKEAMSLPEEASPAPLRTFTVDTLCKLFRIY SNFLRGKLTLYTGEACRRGDR 31APPRLICDSRVLERYILEAREAENVTMGCAQGCSFSENITVPDTKVN The mature amino ProteinFYTWKRMDVGQQALEVWQGLALLSEAILRGQALLANASQPSETPQ acid sequence ofLHVDKAVSSLRSLTSLLRALGAQKEAMSLPEEASPAPLRTFTVDTL cEPOCKLFRIYSNFLRGKLTLYTGEACRRGDR 32MGVRECPALLLLLSLLLPPLGLPALGAPPRLICDSRVLERYILEAREAENVTM Full-length aminoProtein GCAEGCSFGENVTVPDTKVNFYSWKRMEVEQQAVEVWQGLALLSEAILQG acid sequenceof QALLANSSQPSETLRLHVDKAVSSLRSLTSLLRALGAQKEAISPPDAASAAPL eEPORTFAVDTLCKLFRIYSNFLRGKLKLYTGEACRRGDR 33APPRLICDSRVLERYILEAREAENVTMGCAEGCSFGENVTVPDTKVNFYSWK The mature aminoProtein RMEVEQQAVEVWQGLALLSEAILQGQALLANSSQPSETLRLHVDKAVSSLR acidsequence of SLTSLLRALGAQKEAISPPDAASAAPLRTFAVDTLCKLFRIYSNFLRGKLKLY eEPOTGEACRRGDR 34 CCGGCGGTAGTTCAGCAGGGCAGAACGGCGGACTCTAAATCCGCATGGC M.jannaschii tRNA GCTGGTTCAAATCCGGCCCGGCCGGACCA mtRNA_(CUA) ^(Tyr)

TABLE 3 SEQ ID NO: 28 Nucleotide sequence of the suppression expressionconstruct Nat L BB-Opti FEPO in Lucy F for feline erythropoietin 1TCGCGCGTTT CGGTGATGAC GGTGAAAACC TCTGACACAT GCAGCTCCCG GAGACGGTCAAGCGCGCAAA GCCACTACTG CCACTTTTGG AGACTGTGTA CGTCGAGGGC CTCTGCCAGT 61CAGCTTGTCT GTAAGCGGAT GCCGGGAGCA GACAAGCCCG TCAGGGCGCG TCAGCGGGTGGTCGAACAGA CATTCGCCTA CGGCCCTCGT CTGTTCGGGC AGTCCCGCGC AGTCGCCCAC 121TTGGCGGGTG TCGGGGCTGG CTTAACTATG CGGCATCAGA GCAGATTGTA CTGAGAGTGCAACCGCCCAC AGCCCCGACC GAATTGATAC GCCGTAGTCT CGTCTAACAT GACTCTCACG 181ACCATATGCC CGTCCGCGTA CCGGCGCGCC GGATGCCAAT CGATGAATTC CGGTGTGAAATGGTATACGG GCAGGCGCAT GGCCGCGCGG CCTACGGTTA GCTACTTAAG GCCACACTTT 241TACCGCACAG ATGCGTAAGG AGAAAATACC GCATCAGGCG CCATTCGCCA TTCAGGCTGCATGGCGTGTC TACGCATTCC TCTTTTATGG CGTAGTCCGC GGTAAGCGGT AAGTCCGACG 301GCAACTGTTG GGAAGGGCGA TCGGTGCGGG CCTCTTCGCT ATTACGCCAG CTGGCGAAAGCGTTGACAAC CCTTCCCGCT AGCCACGCCC GGAGAAGCGA TAATGCGGTC GACCGCTTTC 361GGGGATGTGC TGCAAGGCGA TTAAGTTGGG TAACGCCAGG GTTTTCCCAG TCACGACGTTCCCCTACACG ACGTTCCGCT AATTCAACCC ATTGCGGTCC CAAAAGGGTC AGTGCTGCAA                                                    tRNA                                             ~~~~~~~~~~~~~~~~~~~~                                                     H1                                             ~~~~~~~~~~~~~~~~~~~~ 421GTAAAACGAC GGCCAGTGAA TTGATGCATC CATCAATTCA TATTTGCATG TCGCTATGTGCATTTTGCTG CCGGTCACTT AACTACGTAG GTAGTTAAGT ATAAACGTAC AGCGATACAC                            tRNA~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                             H1~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 481TTCTGGGAAA TCACCATAAA CGTGAAATGT CTTTGGATTT GGGAATCTTA TAAGTTCTGTAAGACCCTTT AGTGGTATTT GCACTTTACA GAAACCTAAA CCCTTAGAAT ATTCAAGACA                            tRNA~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~     H1                            Hyb1 tRNA~~~~~~~~~~~~~~     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 541ATGAGACCAC TCGGATCCGG TGGGGTAGCG AAGTGGCTAA ACGCGGCGGA CTCTAAATCCTACTCTGGTG AGCCTAGGCC ACCCCATCGC TTCACCGATT TGCGCCGCCT GAGATTTAGG               Hyb1 tRNA ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                     tRNA~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                                            Term                                            ~~~~~~ 601 GCTCCCTTTGGGTTCGGCGG TTCGAATCCG TCCCCCACCA TTTTTTGGAA CCTAGGGAAT CGAGGGAAACCCAAGCCGCC AAGCTTAGGC AGGGGGTGGT AAAAAACCTT GGATCCCTTA 661 TCCGGTGTGAAATACCGCAC AGATGCGTAA GGAGAAAATA CCGCATCAGG CGCCATTCGC AGGCCACACTTTATGGCGTG TCTACGCATT CCTCTTTTAT GGCGTAGTCC GCGGTAAGCG 721 CATTCAGGCTGCGCAACTGT TGGGAAGGGC GATCGGTGCG GGCCTCTTCG CTATTACGCC GTAAGTCCGACGCGTTGACA ACCCTTCCCG CTAGCCACGC CCGGAGAAGC GATAATGCGG 781 AGCTGGCGAAAGGGGGATGT GCTGCAAGGC GATTAAGTTG GGTAACGCCA GGGTTTTCCC TCGACCGCTTTCCCCCTACA CGACGTTCCG CTAATTCAAC CCATTGCGGT CCCAAAAGGG                                                          tRNA                                                          ~~~~~~~                                                          H1                                                          ~~~~~~~ 841AGTCACGACG TTGTAAAACG ACGGCCAGTG AATTGATGCA TCCATCAATT CATATTTGCATCAGTGCTGC AACATTTTGC TGCCGGTCAC TTAACTACGT AGGTAGTTAA GTATAAACGT                            tRNA~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                             H1~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 901TGTCGCTATG TGTTCTGGGA AATCACCATA AACGTGAAAT GTCTTTGGAT TTGGGAATCTACAGCGATAC ACAAGACCCT TTAGTGGTAT TTGCACTTTA CAGAAACCTA AACCCTTAGA                            tRNA~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~           H1                              Hyb1 tRNA~~~~~~~~~~~~~~~~~~~~~~~~~~~      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 961TATAAGTTCT GTATGAGACC ACTCGGATCC GGTGGGGTAG CGAAGTGGCT AAACGCGGCGATATTCAAGA CATACTCTGG TGAGCCTAGG CCACCCCATC GCTTCACCGA TTTGCGCCGC                                                         Term                                                         ~~~~~~                              tRNA~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                     Hyb1 tRNA~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 1021GACTCTAAAT CCGCTCCCTT TGGGTTCGGC GGTTCGAATC CGTCCCCCAC CATTTTTTGGCTGAGATTTA GGCGAGGGAA ACCCAAGCCG CCAAGCTTAG GCAGGGGGTG GTAAAAAACC 1081AAGACGTCGA ATTCCGGTGT GAAATACCGC ACAGATGCGT AAGGAGAAAA TACCGCATCATTCTGCAGCT TAAGGCCACA CTTTATGGCG TGTCTACGCA TTCCTCTTTT ATGGCGTAGT 1141GGCGCCATTC GCCATTCAGG CTGCGCAACT GTTGGGAAGG GCGATCGGTG CGGGCCTCTTCCGCGGTAAG CGGTAAGTCC GACGCGTTGA CAACCCTTCC CGCTAGCCAC GCCCGGAGAA 1201CGCTATTACG CCAGCTGGCG AAAGGGGGAT GTGCTGCAAG GCGATTAAGT TGGGTAACGCGCGATAATGC GGTCGACCGC TTTCCCCCTA CACGACGTTC CGCTAATTCA ACCCATTGCG 1261CAGGGTTTTC CCAGTCACGA CGTTGTAAAA CGACGGCCAG TGAATTGATG CATCCATCAAGTCCCAAAAG GGTCAGTGCT GCAACATTTT GCTGCCGGTC ACTTAACTAC GTAGGTAGTT                              tRNA     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                               H1     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 1321TTCATATTTG CATGTCGCTA TGTGTTCTGG GAAATCACCA TAAACGTGAA ATGTCTTTGGAAGTATAAAC GTACAGCGAT ACACAAGACC CTTTAGTGGT ATTTGCACTT TACAGAAACC                           tRNA~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                 H1                               Hyb1 tRNA~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~      ~~~~~~~~~~~~~~~~~~~ 1381ATTTGGGAAT CTTATAAGTT CTGTATGAGA CCACTCGGAT CCGGTGGGGT AGCGAAGTGGTAAACCCTTA GAATATTCAA GACATACTCT GGTGAGCCTA GGCCACCCCA TCGCTTCACC                            tRNA~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                         Hyb1 tRNA~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 1441CTAAACGCGG CGGACTCTAA ATCCGCTCCC TTTGGGTTCG GCGGTTCGAA TCCGTCCCCCGATTTGCGCC GCCTGAGATT TAGGCGAGGG AAACCCAAGC CGCCAAGCTT AGGCAGGGGG     Term     ~~~~~~~    tRNA ~~~~~~~~~~~ Hyb1 tRNA ~~~~ 1501 ACCATTTTTTGGAACATATG GAATTCCGGT GTGAAATACC GCACAGATGC GTAAGGAGAA TGGTAAAAAACCTTGTATAC CTTAAGGCCA CACTTTATGG CGTGTCTACG CATTCCTCTT 1561 AATACCGCATCAGGCGCCAT TCGCCATTCA GGCTGCGCAA CTGTTGGGAA GGGCGATCGG TTATGGCGTAGTCCGCGGTA AGCGGTAAGT CCGACGCGTT GACAACCCTT CCCGCTAGCC 1621 TGCGGGCCTCTTCGCTATTA CGCCAGCTGG CGAAAGGGGG ATGTGCTGCA AGGCGATTAA ACGCCCGGAGAAGCGATAAT GCGGTCGACC GCTTTCCCCC TACACGACGT TCCGCTAATT 1681 GTTGGGTAACGCCAGGGTTT TCCCAGTCAC GACGTTGTAA AACGACGGCC AGTGAATTGA CAACCCATTGCGGTCCCAAA AGGGTCAGTG CTGCAACATT TTGCTGCCGG TCACTTAACT                                     tRNA                  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                                      H1                  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 1741TGCATCCATC AATTCATATT TGCATGTCGC TATGTGTTCT GGGAAATCAC CATAAACGTGACGTAGGTAG TTAAGTATAA ACGTACAGCG ATACACAAGA CCCTTTAGTG GTATTTGCAC                            tRNA~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                       H1                                  Hyb1 tRNA~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~      ~~~~~~ 1801AAATGTCTTT GGATTTGGGA ATCTTATAAG TTCTGTATGA GACCACTCGG ATCCGGTGGGTTTACAGAAA CCTAAACCCT TAGAATATTC AAGACATACT CTGGTGAGCC TAGGCCACCC                            tRNA~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                         Hyb1 tRNA~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 1861GTAGCGAAGT GGCTAAACGC GGCGGACTCT AAATCCGCTC CCTTTGGGTT CGGCGGTTCGCATCGCTTCA CCGATTTGCG CCGCCTGAGA TTTAGGCGAG GGAAACCCAA GCCGCCAAGC                  Term                  ~~~~~~~          tRNA~~~~~~~~~~~~~~~~~~~~~~~~    Hyb1 tRNA ~~~~~~~~~~~~~~~~~ 1921 AATCCGTCCCCCACCATTTT TTGGAACTTA ATTAAGGCGC GCCGGATGCC AATCGGCCAT TTAGGCAGGGGGTGGTAAAA AACCTTGAAT TAATTCCGCG CGGCCTACGG TTAGCCGGTA 1981 CACCATCCAACGGGAAGGCG ATGAATTCCG GTGTGAAATA CCGCACAGAT GCGTAAGGAG GTGGTAGGTTGCCCTTCCGC TACTTAAGGC CACACTTTAT GGCGTGTCTA CGCATTCCTC 2041 AAAATACCGCATCAGGCGCC ATTCGCCATT CAGGCTGCGC AACTGTTGGG AAGGGCGATC TTTTATGGCGTAGTCCGCGG TAAGCGGTAA GTCCGACGCG TTGACAACCC TTCCCGCTAG 2101 GGTGCGGGCCTCTTCGCTAT TACGCCAGCT GGCGAAAGGG GGATGTGCTG CAAGGCGATT CCACGCCCGGAGAAGCGATA ATGCGGTCGA CCGCTTTCCC CCTACACGAC GTTCCGCTAA 2161 AAGTTGGGTAACGCCAGGGT TTTCCCAGTC ACGACGTTGT AAAACGACGG CCAGTGAATT TTCAACCCATTGCGGTCCCA AAAGGGTCAG TGCTGCAACA TTTTGCTGCC GGTCACTTAA                                      tRNA                    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                                       H1                    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 2221GATGCATCCA TCAATTCATA TTTGCATGTC GCTATGTGTT CTGGGAAATC ACCATAAACGCTACGTAGGT AGTTAAGTAT AAACGTACAG CGATACACAA GACCCTTTAG TGGTATTTGC                        H1~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                            tRNA~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                                                             Hyb1 tRNA                                                             ~~~~ 2281TGAAATGTCT TTGGATTTGG GAATCTTATA AGTTCTGTAT GAGACCACTC GGATCCGGTGACTTTACAGA AACCTAAACC CTTAGAATAT TCAAGACATA CTCTGGTGAG CCTAGGCCAC                            tRNA~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                         Hyb1 tRNA~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 2341GGGTAGCGAA GTGGCTAAAC GCGGCGGACT CTAAATCCGC TCCCTTTGGG TTCGGCGGTTCCCATCGCTT CACCGATTTG CGCCGCCTGA GATTTAGGCG AGGGAAACCC AAGCCGCCAA    Hyb1 tRNA ~~~~~~~~~~~~~~~~~~~           tRNA~~~~~~~~~~~~~~~~~~~~~~~~~~                     Term                   ~~~~~~~ 2401 CGAATCCGTC CCCCACCATT TTTTGGAACCTAGGGAATTC CGGTGTGAAA TACCGCACAG GCTTAGGCAG GGGGTGGTAA AAAACCTTCGATCCCTTAAG GCCACACTTT ATGGCGTGTC 2461 ATGCGTAAGG AGAAAATACC GCATCAGGCGCCATTCGCCA TTCAGGCTGC GCAACTGTTG TACGCATTCC TCTTTTATGG CGTAGTCCGCGGTAAGCGGT AAGTCCGACG CGTTGACAAC 2521 GGAAGGGCGA TCGGTGCGGG CCTCTTCGCTATTACGCCAG CTGGCGAAAG GGGGATGTGC CCTTCCCGCT AGCCACGCCC GGAGAAGCGATAATGCGGTC GACCGCTTTC CCCCTACACG 2581 TGCAAGGCGA TTAAGTTGGG TAACGCCAGGGTTTTCCCAG TCACGACGTT GTAAAACGAC ACGTTCCGCT AATTCAACCC ATTGCGGTCCCAAAAGGGTC AGTGCTGCAA CATTTTGCTG                                              tRNA                                  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                                               H1                                  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 2641GGCCAGTGAA TTGATGCATC CATCAATTCA TATTTGCATG TCGCTATGTG TTCTGGGAAACCGGTCACTT AACTACGTAG GTAGTTAAGT ATAAACGTAC AGCGATACAC AAGACCCTTT                            tRNA~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                             H1~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 2701TCACCATAAA CGTGAAATGT CTTTGGATTT GGGAATCTTA TAAGTTCTGT ATGAGACCACAGTGGTATTT GCACTTTACA GAAACCTAAA CCCTTAGAAT ATTCAAGACA TACTCTGGTG                            tRNA~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~H1                           Hyb1 tRNA~~~     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 2761TCGGATCCGG TGGGGTAGCG AAGTGGCTAA ACGCGGCGGA CTCTAAATCC GCTCCCTTTGAGCCTAGGCC ACCCCATCGC TTCACCGATT TGCGCCGCCT GAGATTTAGG CGAGGGAAAG                                  Term                                 ~~~~~~                 tRNA~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~           Hyb1 tRNA~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 2821 GGTTCGGCGG TTCGAATCCG TCCCCCACCATTTTTTGGAA GACGTCGAAT TCCGGTGTGA CCAAGCCGCC AAGCTTAGGC AGGGGGTGGTAAAAAACCTT CTGCAGCTTA AGGCCACACT 2881 AATACCGCAC AGATGCGTAA GGAGAAAATACCGCATCAGG CGCCATTCGC CATTCAGGGT TTATGGCGTG TCTACGCATT CCTCTTTTATGGCGTAGTCC GCGGTAAGCG GTAAGTCCGA 2941 GCGCAACTGT TGGGAAGGGC GATCGGTGCGGGCCTCTTCG CTATTACGCC AGCTGGCGAA CGCGTTGACA ACCCTTCCCG CTAGCCACGCCCGGAGAAGC GATAATGCGG TCGACCGCTT 3001 AGGGGGATGT GCTGCAAGGC GATTAAGTTGGGTAACGCCA GGGTTTTCCC AGTCACGACG TCCCCCTACA CGACGTTCCG CTAATTCAACCCATTGCGGT CCCAAAAGGG TCAGTGCTGC                                                     tRNA                                               ~~~~~~~~~~~~~~~~~~                                                      H1                                               ~~~~~~~~~~~~~~~~~~ 3061TTGTAAAACG ACGGCCAGTG AATTGATGCA TCCATCAATT CATATTTGCA TGTCGCTATGAACATTTTGC TGCCGGTCAC TTAACTACGT AGGTAGTTAA GTATAAACGT ACAGCGATAC                            tRNA~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                             H1~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 3121TGTTCTGGGA AATCACCATA AACGTGAAAT GTCTTTGGAT TTGGGAATCT TATAAGTTCTACAAGACCCT TTAGTGGTAT TTGCACTTTA CAGAAACCTA AACCCTTAGA ATATTCAAGA                            tRNA~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~      H1                             Hyb1 tRNA~~~~~~~~~~~~~~~~      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 3181GTATGAGACC ACTCGGATCC GGTGGGGTAG CGAAGTGGCT AAACGCGGCG GACTCTAAATCATACTCTGG TGAGCCTAGG CCACCCCATC GCTTCACCGA TTTGCGCCGC CTGAGATTTA                                               Term                                              ~~~~~~                     tRNA~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                Hyb1 tRNA ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~3241 CCGCTCCCTT TGGGTTCGGC GGTTCGAATC CGTCCCCCAC CATTTTTTGG AACATATGGAGGCGAGGGAA ACCCAAGCGG CCAAGCTTAG GCAGGGGGTG GTAAAAAACC TTGTATACCT 3301ATTCCGGTGT GAAATACCGC ACAGATGCGT AAGGAGAAAA TACCGCATCA GGCGCCATTCTAAGGCCACA CTTTATGGCG TGTCTACGCA TTCCTCTTTT ATGGCGTAGT CCGCGGTAAG 3361GCCATTCAGG CTGCGCAACT GTTGGGAAGG GCGATCGGTG CGGGCCTCTT CGCTATTACGCGGTAAGTCC GACGCGTTGA CAACCCTTCC CGCTAGCCAC GCCCGGAGAA GCGATAATGC 3421CCAGCTGGCG AAAGGGGGAT GTGCTGCAAG GCGATTAAGT TGGGTAACGC CAGGGTTTTCGGTCGACCGC TTTCCCCCTA CACGACGTTC CGCTAATTCA ACCCATTGCG GTCCCAAAAG                                                            tRNA                                                            ~~~~~                                                             H1                                                            ~~~~~ 3481CCAGTCACGA CGTTGTAAAA CGACGGCCAG TGAATTGATG CATCCATCAA TTCATATTTGGGTCAGTGCT GCAACATTTT GCTGCCGGTC ACTTAACTAC GTAGGTAGTT AAGTATAAAG                            tRNA~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                             H1~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 3541CATGTCGCTA TGTGTTCTGG GAAATCACCA TAAACGTGAA ATGTCTTTGG ATTTGGGAATGTACAGCGAT ACACAAGACC CTTTAGTGGT ATTTGCACTT TACAGAAACC TAAACCCTTA                            tRNA~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~            H1                              Hyb1 tRNA~~~~~~~~~~~~~~~~~~~~~~~~~~~~      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 3601CTTATAAGTT CTGTATGAGA CCACTCGGAT CCGGTGGGGT AGCGAAGTGG CTAAACGCGGGAATATTCAA GACATACTCT GGTGAGCCTA GGCCACCCCA TCGCTTCACC GATTTGCGCC                                                            Term                                                           ~~~~~~                            tRNA~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                      Hyb1 tRNA~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 3661CGGACTCTAA ATCCGCTCCC TTTGGGTTCG GCGGTTCGAA TCCGTCCCCC ACCATTTTTTGCCTGAGATT TAGGCGAGGG AAACCCAAGC CGCCAAGCTT AGGCAGGGGG TGGTAAAAAA                                      SVO                   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 3721GGAACTTAAT TAAGTACGGG CCTCCAAAAA AGCCTCCTCA CTACTTCTGG AATAGCTCAGCCTTGAATTA ATTCATGCCC GGAGGTTTTT TCGGAGGAGT GATGAAGACC TTATCGAGTC                            SVO~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 3781AGGCAGAGGC GGCCTCGGCC TCTGCATAAA TAAAAAAAAT TAGTCAGCCA TGGGGCGGAGTCCGTCTCCG CCGGAGCCGG AGACGTATTT ATTTTTTTTA ATCAGTCGGT ACCCCGCCTC                            SVO~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 3841AATGGGCGGA ACTGGGCGGA GTTAGGGGCG GGATGGGCGG AGTTAGGGGC GGGACTATGGTTACCCGCCT TGACCCGCCT CAATCCCCGC CCTACCCGCC TCAATCCCCG CCCTGATACC                            SVO~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 3901TTGCTGACTA ATTGAGATGC ATGCTTTGCA TACTTCTGCC TGCTGGGGAG CCTGGGGACTAACGACTGAT TAACTCTACG TACGAAACGT ATGAAGACGG ACGACCCCTC GGACCCCTGA                        SVO                                   CMV~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~         ~~~3961 TTCCACACCT GGTTGCTGAC TAATTGAGAT GCATGCTTTG CATACTTCTG CCCGCGGAGTAAGGTGTGGA CCAACGACTG ATTAACTCTA CGTACGAAAC GTATGAAGAC GGGCGCCTCA                            CMV~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 4021TATTAATAGT AATCAATTAC GGGGTCATTA GTTCATAGCC CATATATGGA GTTCCGCGTTATAATTATCA TTAGTTAATG CCCCAGTAAT CAAGTATCGG GTATATACCT CAAGGCGCAA                            CMV~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 4081ACATAACTTA CGGTAAATGG CCCGCCTGGC TGACCGCCCA ACGACCCCCG CCCATTGACGTGTATTGAAT GCCATTTACC GGGCGGACCG ACTGGCGGGT TGCTGGGGGC GGGTAACTGC                            CMV~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 4141TCAATAATGA CGTATGTTCC CATAGTAACG CCAATAGGGA CTTTCCATTG ACGTCAATGGAGTTATTACT GCATACAAGG GTATCATTGC GGTTATCCCT GAAAGGTAAC TGCAGTTACC                            CMV~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 4201GTGGAGTATT TACGGTAAAC TGCCCACTTG GGAGTACATC AAGTGTATCA TATGCCAAGTCACCTCATAA ATGCCATTTG ACGGGTGAAC CGTCATGTAG TTCACATAGT ATACGGTTCA                            CMV~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 4261ACGCCCCCTA TTGACGTCAA TGACGGTAAA TGGCCCGCCT GGCATTATGC CCAGTACATGTGCGGGGGAT AACTGCAGTT ACTGCCATTT ACCGGGCGGA CCGTAATACG GGTCATGTAC                            CMV~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 4321ACCTTATGGG ACTTTCCTAC TTGGCAGTAC ATCTACGTAT TAGTCATCGC TATTACCATGTGGAATACCC TGAAAGGATG AACCGTCATG TAGATGCATA ATCAGTAGCG ATAATGGTAC                            CMV~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 4381GTGATGCGGT TTTGGCAGTA CATCAATGGG CGTGGATAGC GGTTTGACTC ACGGGGATTTCACTACGCCA AAACCGTCAT GTAGTTACCC GCACCTATCG CCAAACTGAG TGCCCCTAAA                            CMV~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 4441CCAAGCCTCC ACCCCATTGA CGTCAATGGG AGTTTGTTTT GGCACCAAAA TCAACGGGACGGTTCGGAGG TGGGGTAACT GCAGTTACCC TCAAACAAAA CCGTGGTTTT AGTTGCCCTG                            CMV~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 4501TTTCCAAAAT GTCGTAACAA CTCCGCCCCA TTGACGCAAA TGGGCGGTAG GCGTGTACGGAAAGGTTTTA CAGCATTGTT GAGGCGGGGT AACTGCGTTT ACCCGCCATC CGCACATGCC                            CMV~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 4561TGGGAGGTCT ATATAAGCAG AGCTCTCTGG CTAACTAGAG AACCCACTGC TTACTGGCTTACCCTCCAGA TATATTCGTC TCGAGAGACC GATTGATCTC TTGGGTGACG AATGACCGAA   CMV                                 Nat L~~~~~~~~~             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 4621ATCGAAATTA CTAGTCCACC ATGGGGTCGT GCGAATGTCC TGCCCTGCTG CTTCTGCTATTAGCTTTAAT GATCAGGTGG TACCCCAGCA CGCTTACAGG ACGGGACGAC GAAGACGATA               Nat L ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                                              BB-Opti FEPO                                         ~~~~~~~~~~~~~~~~~~~~~~~~ 4681CTTTGCTGCT GCTTCCCCTG GGCCTCCCAG TCCTGGGCGC CCCCCCTCGC CTCATCTGTGGAAACGACGA CGAAGGGGAC CCGGAGGGTC AGGACCCGCG GGGGGGAGCG GAGTAGACAC                        BB-Opti FEPO~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 4741ACAGCCGAGT CCTGGAGAGG TACATTCTGG AGGCCAGGGA GGCCGAAAAT GTGACCATGGTGTCGGCTCA GGACCTCTCC ATGTAAGACC TCCGGTCCCT CCGGCTTTTA CACTGGTACC                        BB-Opti FEPO~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 4801GCTGCGCTGA AGGCTGCAGC TTCAGTGAGA ATATCACCGT TCCGGACACC AAGGTCAACTCGACGCGACT TCCGACGTCG AAGTCACTCT TATAGTGGCA AGGCCTGTGG TTCCAGTTGA                        BB-Opti FEPO~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 4861TCTATACCTG GAAGAGGATG GACGTCGGGC AGCAGGCTGT GGAAGTCTGG CAGGGCCTCGAGATATGGAC CTTCTCCTAC CTGCAGCCCG TCGTCCGACA CCTTCAGACC GTCCCGGAGC                        BB-Opti FEPO~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 4921CCCTCCTCAG CGAAGCCATC CTGCGGGGCC AGGCCCTGCT GGCCAACTCC TCCCAGCCCTGGGAGGAGTC GCTTCGGTAG GACGCCCCGG TCCGGGACGA CCGGTTGAGG AGGGTCGGGA                        BB-Opti FEPO~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 4981CTGAGACCCT GCAGCTGCAT GTCGACAAGG CCGTCAGCAG CCTGCGCAGC CTCACCTCCCGACTCTGGGA CGTCGACGTA CAGCTGTTCC GGCAGTCGTC GGACGCGTCG GAGTGGAGGG                        BB-Opti FEPO~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 5041TGCTGCGCGC ACTGGGAGCC CAGAAGGAAG CCACCTCCCT TCCCGAGGCA ACCTCTGCCGACGACGCGCG TGACCCTCGG GTCTTCCTTC GGTGGAGGGA AGGGCTCCGT TGGAGACGGC                        BB-Opti FEPO~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 5101CCCCCTTAAG AACCTTCACT GTGGACACTT TGTGCAAGCT TTTCCGAATC TACTCCAACTGGGGGAATTC TTGGAAGTGA CACCTGTGAA ACACGTTCGA AAAGGCTTAG ATGAGGTTGA                       BB-Opti FEPO~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 5161TCCTGCGGGG CAAGCTGACG CTGTACACAG GGGAGGCCTG CCGAAGAGGA GACAGGTGAGAGGACGCCCC GTTCGACTGC GACATGTGTC CCCTCCGGAC GGCTTCTCCT CTGTCCACTC                                      BGH                   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 5221CGGCCGCATC AGCCTCGACT GTGCCTTCTA GTTGCCAGCC ATCTGTTGTT TGCCCCTCCCGCCGGCGTAG TCGGAGCTGA CACGGAAGAT CAACGGTCGG TAGACAACAA ACGGGGAGGG                            BGH~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 5281CCGTGCCTTC CTTGACCCTG GAAGGTGCCA CTCCCACTGT CCTTTCCTAA TAAAATGAGGGGCACGGAAG GAACTGGGAC CTTCCACGGT GAGGGTGACA GGAAAGGATT ATTTTACTCC                            BGH~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 5341AAATTGCATC GCATTGTCTG AGTAGGTGTC ATTCTATTCT GGGGGGTGGG GTGGGGCAGGTTTAACGTAG CGTAACAGAC TCATCCACAG TAAGATAAGA CCCCCCACCC CACCCCGTCC                          BGH~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 5401ACAGCAAGGG GGAGGATTGG GAAGACAATA GCAGGCATGC TGGGGATGCG GTGGGCTCTATGTCGTTCCC CCTCCTAACC CTTCTGTTAT CGTCCGTACG ACCCCTACGC CACCCGAGAT                                              Beta                                  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 5461TGGCTTCTGA GGCGGAAAGA ACCAGTGTAC AGCTTTGCTT CTCAATTTCT TATTTGCATAACCGAAGACT CCGCCTTTCT TGGTCACATG TCGAAACGAA GAGTTAAAGA ATAAACGTAT                            Beta~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 5521ATGAGAAAAA AAGGAAAATT AATTTTAACA CCAATTCAGT AGTTGATTGA GCAAATGCGTTACTCTTTTT TTCCTTTTAA TTAAAATTGT GGTTAAGTCA TCAACTAACT CGTTTACGCA                            Beta~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 5581TGCCAAAAAG GATGCTTTAG AGACAGTGTT CTCTGCACAG ATAAGGACAA ACATTATTCAACGGTTTTTC CTACGAAATC TCTGTCACAA GAGACGTGTC TATTCCTGTT TGTAATAAGT                            Beta~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 5641GAGGGAGTAC CCAGAGCTGA GACTCCTAAG CCAGTGAGTG GCACAGCATC CAGGGAGAAACTCCCTCATG GGTCTCGACT CTGAGGATTC GGTCACTCAC CGTGTCGTAG GTCCCTCTTT                            Beta~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 5701TATGCTTGTC ATCACCGAAG CCTGATTCCG TAGAGCCACA CCCTGGTAAG GGCCAATCTGATACGAACAG TAGTGGCTTC GGACTAAGGC ATCTCGGTGT GGGACCATTC CCGGTTAGAC                            Beta~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 5761CTCACACAGG ATAGAGAGGG CAGGAGCCAG GGCAGAGCAT ATAAGGTGAG GTAGGATCAGGAGTGTGTCC TATCTCTCCC GTCCTCGGTC CCGTCTCGTA TATTCCACTC CATCCTAGTC                Beta ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 5821TTGCTCCTCA CATTTGCTTC TGACATAGTT GTGTTGGGAG CTTGGATAGC TTGGGGGGGGAACGAGGAGT GTAAACGAAG ACTGTATCAA CACAACCCTC GAACCTATCG AACCCCCCCC 5881GACAGCTCAG GGCTGCGATT TCGCGCCAAC TTGACGGCAA TCCTAGCGTG AAGGCTGGTACTGTCGAGTC CCGACGCTAA AGCGCGGTTG AACTGCCGTT AGGATCGCAC TTCCGACCAT                                      OptEcAFRS                        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 5941GGATTTTATC CCTCGAGCCA CCATGGCCTC CAGCAACCTG ATCAAGCAGC TCCAGGAGAGCCTAAAATAG GGAGCTCGGT GGTACCGGAG GTCGTTGGAC TAGTTCGTCG AGGTCCTCTC                         OptEcAFRS~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 6001GGGCCTCGTG GCTCAGGTCA CCGACGAAGA AGCACTCGCT GAAAGACTGG CCCAGGGACCCCCGGAGCAC CGAGTCCAGT GGCTGCTTCT TCGTGAGCGA CTTTCTGACC GGGTCCCTGG                         OptEcAFRS~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 6061CATTGCACTG ATCTGCGGGT TCGATCCTAC AGCCGACTCT CTCCACCTGG GTCATCTCGTGTAACGTGAC TAGACGCCCA AGCTAGGATG TCGGCTGAGA GAGGTGGACC CAGTAGAGCA                         OptEcAFRS~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 6121GCCACTGCTG TGTCTCAAAC GGTTTCAGCA GGCTGGCCAC AAGCCCGTCG CACTGGTGGGCGGTGACGAC ACAGAGTTTG CCAAAGTCGT CCGACCGGTG TTCGGGCAGC GTGACCACCC                         OptEcAFRS~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 6181AGGTGCTACT GGGCTGATTG GCGATCCTAG TTTCAAAGCC GCAGAGCGCA AGCTCAATACTCCACGATGA CCCGACTAAC CGCTAGGATC AAAGTTTCGG CGTCTCGCGT TCGAGTTATG                         OptEcAFRS~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 6241CGAGGAGACA GTGCAGGAAT GGGTCGACAA AATCCGAAAG CAGGTCGCCC CATTTCTGGAGCTCCTCTGT CACGTCCTTA CCCAGCTGTT TTAGGCTTTC GTCCAGCGGG GTAAAGACCT                         OptEcAFRS~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 6301TTTCGACTGC GGAGAGAACT CAGCTATTGC CGCAAATAAC TACGATTGGT TTGGGAATATAAAGCTGACG CCTCTCTTGA GTCGATAACG GCGTTTATTG ATGCTAACCA AACCCTTATA                         OptEcAFRS~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 6361GAACGTCCTC ACTTTCCTGC GTGACATCGG TAAACATTTT TCCGTGAATC AGATGATTAACTTGCAGGAG TGAAAGGACG CACTGTAGCC ATTTGTAAAA AGGCACTTAG TCTACTAATT                         OptEcAFRS~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 6421CAAGGAAGCT GTGAAGCAGA GGCTGAATAG AGAGGGCCAG GGAATCAGCT TCACCGAATTGTTCCTTCGA CACTTCGTCT CCGACTTATC TCTCCCGGTC CCTTAGTCGA AGTGGCTTAA                         OptEcAFRS~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 6481TTCTTATAAT CTCCTGCAGG GGTACGGTAT GGCCTGTGCA AACAAACAGT ATGGCGTCGTAAGAATATTA GAGGACGTCC CCATGCCATA CCGGACACGT TTGTTTGTCA TACCGCAGCA                         OptEcAFRS~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 6541GCTGCAGATT GGAGGCAGTG ATCAGTGGGG GAACATCACA TCAGGTATTG ACCTCACTCGCGACGTCTAA CCTCCGTCAC TAGTCACCCC CTTGTAGTGT AGTCCATAAC TGGAGTGAGC                         OptEcAFRS~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 6601GCGCCTGCAC CAGAATCAGG TCTTTGGACT CACCGTGCCC CTGATCACAA AGGCTGATGGCGCGGACGTG GTCTTAGTCC AGAAACCTGA GTGGCACGGG GACTAGTGTT TCCGACTACC                         OptEcAFRS~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 6661CACAAAATTT GGTAAGACCG AGGGTGGAGC CGTGTGGCTG GACCCTAAAA AGACATCCCCGTGTTTTAAA CCATTCTGGC TCCCACCTCG GCACACCGAC CTGGGATTTT TCTGTAGGGG                         OptEcAFRS~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 6721ATACAAATTC TATCAGTTTT GGATCAACAC TGCAGATGCT GACGTCTACC GATTCCTCAATATGTTTAAG ATAGTCAAAA CCTAGTTGTG ACGTCTACGA CTGCAGATGG CTAAGGAGTT                         OptEcAFRS~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 6781GTTTTTCACC TTTATGAGCA TTGAGGAAAT CAATGCCCTG GAGGAAGAGG ATAAGAACTCCAAAAAGTGG AAATACTCGT AACTCCTTTA GTTACGGGAC CTCCTTCTCC TATTCTTGAG                         OptEcAFRS~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 6841TGGCAAAGCT CCCCGTGCAC AGTATGTGCT CGCCGAACAG GTCACAAGGC TGGTGCATGGACCGTTTCGA GGGGCACGTG TCATACACGA GCGGCTTGTC CAGTGTTCCG ACCACGTACC                         OptEcAFRS~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 6901GGAGGAAGGT CTGCAGGCTG CCAAGAGAAT TACTGAGTGC CTCTTCAGTG GCTCACTGTCCCTCCTTCCA GACGTCCGAC GGTTCTCTTA ATGACTCACG GAGAAGTCAC CGAGTGACAG                         OptEcAFRS~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 6961CGCACTGAGC GAAGCTGACT TTGAGCAGCT CGCCCAGGAT GGAGTGCCTA TGGTCGAGATGCGTGACTCG CTTCGACTGA AACTCGTCGA GCGGGTCCTA CCTCACGGAT ACCAGCTCTA                         OptEcAFRS~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 7021GGAAAAAGGC GCAGACCTGA TGCAGGCTCT CGTGGATTCT GAGCTGCAGC CAAGTCGGGGCCTTTTTCCG CGTCTGGACT ACGTCCGAGA GCACCTAAGA CTCGACGTCG GTTCAGCCCC                         OptEcAFRS~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 7081GCAGGCCCGC AAGACCATCG CATCAAATGC TATTACAATC AACGGTGAAA AACAGTCCGACGTCCGGGCG TTCTGGTAGC GTAGTTTACG ATAATGTTAG TTGCCACTTT TTGTCAGGCT                         OptEcAFRS~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 7141CCCCGAGTAC TTCTTTAAGG AAGAGGATCG ACTGTTCGGA CGTTTTACCC TCCTGAGGAGGGGGCTCATG AAGAAATTCC TTCTCCTAGC TGACAAGCCT GCAAAATGGG AGGACTCCTC              OptEcAFRS                              IRES~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~       ~~~~~~~~~~~~~~~~~~ 7201AGGCAAAAAG AATTATTGTC TGATTTGCTG GAAGTGATCT AGAGGCCGCG CAGTTAACGCTCCGTTTTTC TTAATAACAG ACTAAACGAC CTTCACTAGA TCTCCGGCGC GTCAATTGCG                            IRES~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 7261CGCCCCTCTC CCTCCCCCCC CCTAACGTTA CTGGCCGAAG CCGCTTGGAA TAAGGCCGGTGCGGGGAGAG GGAGGGGGGG GGATTGCAAT GACCGGCTTC GGCGAACCTT ATTCCGGCCA                            IRES~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 7321GTGCGTTTGT CTATATGTTA TATTCCACCA TATTGCCGTC TATTGGCAAT GTGAGGGCCCCACGCAAACA GATATACAAT ATAAGGTGGT ATAACGGCAG ATAACCGTTA CACTCCCGGG                            IRES~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 7381GGAAACCTGG CCCTGTCTTC TTGACGAGCA TTCCTAGGGG TCTTTCCCCT CTCGCCAAAGCCTTTGGACC GGGACAGAAG AACTGCTCGT AAGGATCCCC AGAAAGGGGA GAGCGGTTTC                            IRES~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 7441GAATGCAAGG TCTGTTGAAT GTCGTGAAGG AAGCAGTTCC TCTGGAAGCT TCTTGAAGACCTTACGTTCC AGACAACTTA CAGCACTTCC TTCGTCAAGG AGACCTTCGA AGAACTTCTG                            IRES~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 7501AAACAACGTC TGTAGCGACC CTTTGCAGGC AGCGGAACCC CCCACCTGGC GACAGGTGCCTTTGTTGCAG ACATCGCTGG GAAACGTCCG TCGCCTTGGG GGGTGGACCG CTGTCCACGG                            IRES~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 7561TCTGCGGCCA AAAGCCACGT GTATAAAATA CACCTGCAAA GGCGGCACAA CCCCAGTGCGAGACGCCGGT TTTCGGTGCA CATATTTTAT GTGGACGTTT CCGCCGTGTT GGGGTCACGC                            IRES~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 7621ACGTTGTGAG TTGGATAGTT GTGGAAAGAG TCAAATGGCT CTCCTCAAGC GTATTCAACATGCAACACTC AACCTATCAA CACCTTTCTC AGTTTACCGA GAGGAGTTCG CATAAGTTGT                            IRES~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 7681AGGGGCTGAA GGATGCCCAG AAGGTACCCC ATTGTATGGG ATCTGATCTG GGGCCTCGGTTCCCCGACTT CCTACGGGTC TTCCATGGGG TAACATACCC TAGACTAGAC CCCGGAGCCA                            IRES~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 7741ACACATGCTT TACATGTGTT TAGTCGAGGT TAAAAAAACG TCTAGGCCCC CCGAACCACGTGTGTACGAA ATGTACACAA ATCAGCTCCA ATTTTTTTGC AGATCCGGGG GGCTTGGTGC                    IRES~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 7801 GGGACGTGGTATTCCTTTGA AAAACACGAT GATAATATGG CCACACCCGT CCGAGATCAC CCCTGCACCATAAGGAAACT TTTTGTGCTA CTATTATACC GGTGTGGGCA GGCTCTAGTG                                   DHFR             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 7861CCTCGAGCCA CCATGGTTCG ACCATTGAAC TGCATCGTCG CCGTGTCCCA AAATATGGGGGGAGCTCGGT GGTACCAAGC TGGTAACTTG ACGTAGCAGC GGCACAGGGT TTTATACCCC                            DHFR~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 7921ATTGGCAAGA ACGGAGACCT ACCCTGGCCT CCGCTCAGGA ACGAGTTCAA GTACTTCCAATAACCGTTCT TGCCTCTGGA TGGGACCGGA GGCGAGTCCT TGCTCAAGTT CATGAAGGTT                            DHFR~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 7981AGAATGACCA CAACCTCTTC AGTGGAAGGT AAACAGAATC TGGTGATTAT GGGTAGGAAATCTTACTGGT GTTGGAGAAG TCACCTTCCA TTTGTCTTAG ACCACTAATA CCCATCCTTT                            DHFR~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 8041ACCTGGTTCT CCATTCCTGA GAAGAATCGA CCTTTAAAGG ACAGAATTAA TATAGTTCTCTGGACCAAGA GGTAAGGACT CTTCTTAGCT GGAAATTTCC TGTCTTAATT ATATCAAGAG                            DHFR~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 8101AGTAGAGAAC TCAAAGAACC ACCACGAGGA GCTCATTTTC TTGCCAAAAG TTTGGATGATTCATCTCTTG AGTTTCTTGG TGGTGCTCCT CGAGTAAAAG AACGGTTTTC AAACCTACTA                            DHFR~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 8161GCCTTAAGAC TTATTGAACA ACCGGAATTG GCAAGTAAAG TAGACATGGT TTGGATAGTCCGGAATTCTG AATAACTTGT TGGCCTTAAC CGTTCATTTC ATCTGTACCA AACCTATCAG                            DHFR~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 8221GGAGGCAGTT CTGTTTACCA GGAAGCCATG AATCAACCAG GCCACCTCAG ACTCTTTGTGCCTCCGTCAA GACAAATGGT CCTTCGGTAC TTAGTTGGTC CGGTGGAGTC TGAGAAACAC                            DHFR~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 8281ACAAGGATCA TGCAGGAATT TGAAAGTGAC ACGTTTTTCC CAGAAATTGA TTTGGGGAAATGTTCCTAGT ACGTCCTTAA ACTTTCACTG TGCAAAAAGG GTCTTTAACT AAACCCCTTT                            DHFR~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 8341TATAAACTTC TCCCAGAATA CCCAGGCGTC CTCTCTGAGG TCCAGGAGGA AAAAGGCATCATATTTGAAG AGGGTCTTAT GGGTCCGCAG GAGAGACTCC AGGTCCTCCT TTTTCCGTAG                DHFR                                 IRES~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~       ~~~~~~~~~~~~~~~~~~~ 8401AAGTATAAGT TTGAAGTCTA CGAGAAGAAA GACTAATCTA GAGGCCGCGC ACTTAACGCCTTCATATTCA AACTTCAGAT GCTCTTCTTT CTGATTAGAT CTCCGGCGCG TGAATTGCGG                            IRES~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 8461GCCCCTCTCC CTCCCCCCCC CCTAACGTTA CTGGCCGAAG CCGCTTGGAA TAAGGCCGGTCGGGGAGAGG GAGGGGGGGG GGATTGCAAT GACCGGCTTC GGCGAACCTT ATTCCGGCCA                            IRES~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 8521GTGCGTTTGT CTATATGTTA TTTTCCACCA TATTGCCGTC TTTTGGCAAT GTGAGGGCCCCACGCAAACA GATATACAAT AAAAGGTGGT ATAACGGCAG AAAACCGTTA CACTCCCGGG                            IRES~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 8581GGAAACCTGG CCCTGTCTTC TTGACGAGCA TTCCTAGGGG TCTTTCCCCT CTCGCCAAAGCCTTTGGACC GGGACAGAAG AACTGCTCGT AAGGATCCCC AGAAAGGGGA GAGCGGTTTC                            IRES~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 8641GAATGCAAGG TCTGTTGAAT GTCGTGAAGG AAGCAGTTCC TCTGGAAGCT TCTTGAAGACCTTACGTTCC AGACAACTTA CAGCACTTCC TTCGTCAAGG AGACCTTCGA AGAACTTCTG                            IRES~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 8701AAACAACGTC TGTAGCGACC CTTTGCAGGC AGCGGAACCC CCCACCTGGC GACAGGTGCCTTTGTTGCAG ACATCGCTGG GAAACGTCCG TCGCCTTGGG GGGTGGACCG CTGTCCACGG                            IRES~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 8761TCTGCGGCCA AAAGCCACGT GTATAAGATA CACCTGCAAA GGCGGCACAA CCCCAGTGCCAGACGCCGGT TTTCGGTGCA CATATTCTAT GTGGACGTTT CCGCCGTGTT GGGGTCACGG                            IRES~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 8821ACGTTGTGAG TTGGATAGTT GTGGAAAGAG TCAAATGGCT CTCCTCAAGC GTATTCAACATGCAACACTC AACCTATCAA CACCTTTCTC AGTTTACCGA GAGGAGTTCG CATAAGTTGT                            IRES~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 8881AGGGGCTGAA GGATGCCCAG AAGGTACCCC ATTGTATGGG ATCTGATCTG GGGCCTCGGTTCCCCGACTT CCTACGGGTC TTCCATGGGG TAACATACCC TAGACTAGAC CCCGGAGCCA                            IRES~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 8941ACACATGCTT TACATGTGTT TAGTCGAGGT TAAAAAAACG TCTAGGCCCC CCGAACCACGTGTGTACGAA ATGTACACAA ATCAGCTCCA ATTTTTTTGC AGATCCGGGG GGCTTGGTGC                    IRES                                   Neo~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~           ~~~~~~~~~9001 GGGACGTGGT TTTCCTTTGA AAAACACGAT GATAATATGG CCACAAGATC TATGCTTGAACCCTGCACCA AAAGGAAACT TTTTGTGCTA CTATTATACC GGTGTTCTAG ATACGAACTT                            Neo~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 9061CAAGATGGAT TGCACGCAGG TTCTCCGGCC GCTTGGGTGG AGAGGCTATT CGGCTATGACGTTCTACCTA ACGTGCGTCC AAGAGGCCGG CGAACCCACC TCTCCGATAA GCCGATACTG                            Neo~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 9121TGGGCACAAC AGACAATCGG CTGCTCTGAT GCCGCCGTGT TCCGGCTGTC AGCGCAGGGGACCCGTGTTG TCTGTTAGCC GACGAGACTA CGGCGGCACA AGGCCGACAG TCGCGTCCCC                            Neo~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 9181CGCCCGGTTC TTTTTGTCAA GACCGACCTG TCCGGTGCCC TGAATGAACT GCAGGACGAGGCGGGCCAAG AAAAACAGTT CTGGCTGGAC AGGCCACGGG ACTTACTTGA CGTCCTGCTC                            Neo~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 9241GCAGCGCGGC TATCGTGGCT GGCCACGACG GGCGTTCCTT GCGCAGCTGT GCTCGACGTTCGTCGCGCCG ATAGCACCGA CCGGTGCTGC CCGCAAGGAA CGCGTCGACA CGAGCTGCAA                            Neo~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 9301GTCACTGAAG CGGGAAGGGA CTGGCTGCTA TTGGGCGAAG TGCCGGGGCA GGATCTCCTGCAGTGACTTC GCCCTTCCCT GACCGACGAT AACCCGCTTC ACGGCCCCGT CCTAGAGGAC                            Neo~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 9361TCATCTCACC TTGCTCCTGC CGAGAAAGTA TCCATCATGG CTGATGCAAT GCGGCGGCTGAGTAGAGTGG AACGAGGACG GCTCTTTCAT AGGTAGTACC GACTACGTTA CGCCGCCGAC                            Neo~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 9421CATACGCTTG ATCCGGCTAC CTGCCCATTC GACCACCAAG CGAAACATCG CATCGAGCGAGTATGCGAAC TAGGCCGATG GACGGGTAAG CTGGTGGTTC GCTTTGTAGC GTAGCTCGCT                            Neo~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 9481GCACGTACTC GGATGGAAGC CGGTCTTGTC GATCAGGATG ATCTGGACGA AGAGCATCAGCGTGCATGAG CCTACCTTCG GCCAGAACAG CTAGTCCTAC TAGACCTGCT TCTCGTAGTC                            Neo~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 9541GGGCTCGCGC CAGCCGAACT GTTCGCCAGG CTCAAGGCGC GCATGCCCGA CGGCGAGGATCCCGAGCGCG GTCGGCTTGA CAAGCGGTCC GAGTTCCGCG CGTACGGGCT GCCGCTCCTA                            Neo~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 9601CTCGTCGTGA CCCATGGCGA TGCCTGCTTG CCGAATATCA TGGTGGAAAA TGGCCGCTTTGAGCAGCACT GGGTACCGCT ACGGACGAAC GGCTTATAGT ACCACCTTTT ACCGGCGAAA                            Neo~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 9661TCTGGATTCA TCGACTGTGG CCGGCTGGGT GTGGCGGACC GCTATCAGGA CATAGCGTTGAGACCTAAGT AGCTGACACC GGCCGACCCA CACCGCCTGG CGATAGTCCT GTATCGCAAC                            Neo~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 9721GCTACCCGTG ATATTGCTGA AGAGCTTGGC GGCGAATGGG CTGACCGCTT CCTCGTGCTTCGATGGGCAC TATAACGACT TCTCGAACCG CCGCTTACCC GACTGGCGAA GGAGCACGAA                            Neo~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 9781TACGGTATCG CCGCTCCCGA TTCGCAGCGC ATCGCCTTCT ATCGCCTTCT TGACGAGTTCATGCCATAGC GGCGAGGGCT AAGCGTCGCG TAGCGGAAGA TAGCGGAAGA ACTGCTCAAG  Neo~~~~~~ 9841 TTCTGACAAT TGCACGGGCT ACGAGATTTC GATTCCACCG CCGCCTTCTATGAAAGGTTG AAGACTGTTA ACGTGCCCGA TGCTCTAAAG CTAAGGTGGC GGCGGAAGATACTTTCCAAC 9901 GGCTTCGGAA TCGTTTTCCG GGACGCCGGC TGGATGATCC TCCAGCGCGGGGATCTCATG CCGAAGCCTT AGCAAAAGGC CCTGCGGCCG ACCTACTAGG AGGTCGCGCCCCTAGAGTAC                                      SV40 PolyA                       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 9961CTGGAGTTCT TCGCCCACCC CAACTTGTTT ATTGCAGCTT ATAATGGTTA CAAATAAAGCGACCTCAAGA AGCGGGTGGG GTTGAACAAA TAACGTCGAA TATTACCAAT GTTTATTTCG                         SV40 PolyA~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 10021AATAGCATCA CAAATTTCAC AAATAAAGCA TTTTTTTCAC TGCATTCTAG TTGTGGTTTGTTATCGTAGT GTTTAAAGTG TTTATTTCGT AAAAAAAGTG ACGTAAGATC AACACCAAAC          SV40 PolyA ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 10081 TCCAAACTCATCAATGTATC TTATCATGTC GGTTACCCCC GTCCGACATG TGAGCAAAAG AGGTTTGAGTAGTTACATAG AATAGTACAG CCAATGGGGG CAGGCTGTAC ACTCGTTTTC                                                   ~~~~~~~~~                                                      pUC Ori 10141GCCAGCAAAA GGCCAGGAAC CGTAAAAAGG CCGCGTTGCT GGCGTTTTTC CATAGGCTCCCGGTCGTTTT CCGGTCCTTG GCATTTTTCC GGCGCAACGA CCGCAAAAAG GTATCCGAGG~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                          pUC Ori 10201 GCCCCCCTGA CGAGCATCAC AAAAATCGACGCTCAAGTCA GAGGTGGCGA AACCCGACAG CGGGGGGACT GCTCGTAGTG TTTTTAGCTGCGAGTTCAGT CTCCACCGCT TTGGGCTGTC~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                          pUC Ori 10261 GACTATAAAG ATACCAGGCG TTTCCCCCTGGAAGCTCCCT CGTGCGCTCT CCTGTTCCGA CTGATATTTC TATGGTCCGC AAAGGGGGACCTTCGAGGGA GCACGCGAGA GGACAAGGCT~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                          pUC Ori 10321 CCCTGCCGCT TACCGGATAC CTGTCCGCCTTTCTCCCTTC GGGAAGCGTG GCGCTTTCTC GGGACGGCGA ATGGCCTATG GACAGGCGGAAAGAGGGAAG CCCTTCGCAC CCCGAAAGAG~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                          pUC Ori 10381 ATAGCTCACG CTGTAGGTAT CTCAGTTCGGTGTAGGTCGT TCGCTCCAAG CTGGGCTGTG TATCGAGTGC GACATCCATA GAGTCAAGCCACATCCAGCA AGCGAGGTTC GACCCGACAC~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                          pUC Ori 10441 TGCACGAACC CCCCGTTCAG CCCGACCGCTGCGCCTTATC CGGTAACTAT CGTCTTGAGT ACGTGCTTGG GGGGCAAGTC GGGCTGGCGACGCGGAATAG GCCATTGATA GCAGAACTCA~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                          pUC Ori 10501 CCAACCCGGT AAGACACGAC TTATCGCCACTGGCAGCAGC CACTGGTAAC AGGATTAGCA GGTTGGGCCA TTCTGTGCTG AATAGCGGTGACCGTCGTCG GTGACCATTG TCCTAATCGT~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                          pUC Ori 10561 GAGCGAGGTA TGTAGGCGGT GCTACAGAGTTCTTGAAGTG GTGGCCTAAC TACGGCTACA CTCGCTCCAT ACATCCGCCA CGATGTCTCAAGAACTTCAC CACCGGATTG ATGCCGATGT~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                          pUC Ori 10621 CTAGAAGAAC AGTATTTGGT ATCTGCGCTCTGCTGAAGCC AGTTACCTTC GGAAAAAGAG GATCTTCTTG TCATAAACCA TAGACGCGAGACGACTTCGG TCAATGGAAG CCTTTTTCTC~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                          pUC Ori 10681 TTGGTAGCTC TTGATCCGGC AAACAAACCACCGCTGGTAG CGGTGGTTTT TTTGTTTGCA AACCATCGAG AACTAGGCCG TTTGTTTGGTGGCGACCATC GCCACCAAAA AAACAAACGT~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                          pUC Ori 10741 AGCAGCAGAT TACGCGCAGA AAAAAAGGATCTCAAGAAGA TCCTTTGATC TTTTCTACGG TCGTCGTCTA ATGCGCGTCT TTTTTTCCTAGAGTTCTTCT AGGAAACTAG AAAAGATGCC~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                          pUC Ori 10801 GGTCTGACGC TCAGTGGAAC GAAAACTCACGTTAAGGGAT TTTGGTCATG AGATTATCAA CCAGACTGCG AGTCACCTTG CTTTTGAGTGCAATTCCCTA AAACCAGTAC TCTAATAGTT ~ 10861 AAAGGATCTT CACCTAGATCGTTTTAAATT AAAAATGAAG TTTTAAATCA ATCTAAAGTA TTTCCTAGAA GTGGATCTAGGAAAATTTAA TTTTTACTTC AAAATTTAGT TAGATTTCAT 10921 TATATGAGTA AACTTGGTCTGACAGTTACC AATGCTTAAT CAGTGAGGCA CCTATCTCAG ATATACTCAT TTGAACCAGACTGTCAATGG TTACGAATTA GTCACTCCGT GGATAGAGTC                           ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                                           Amp 10981 CGATCTGTCTATTTCGTTCA TCCATAGTTG CCTGACTCCC CGTCGTGTAG ATAACTACGA GCTAGACAGATAAAGCAAGT AGGTATCAAC GGACTGAGGG GCAGCACATC TATTGATGCT~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                            Amp 11041 TACGGGAGGG CTTACCATCT GGCCCCAGTGCTGCAATGAT ACCGCGAGAC CCACGCTCAC ATGCCCTCCC GAATGGTAGA CCGGGGTCACGACGTTACTA TGGCGCTCTG GGTGCGAGTG~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                            Amp 11101 CGGCTCCAGA TTTATCAGCA ATAAACCAGCCAGCCGGAAG GGCCGAGCGC AGAAGTGGTC GCCGAGGTCT AAATAGTCGT TATTTGGTCGGTCGGCCTTC CCGGCTCGCG TCTTCACCAG~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                            Amp 11161 CTGCAACTTT ATCCGCCTCC ATCCAGTCTATTAATTGTTG CCGGGAAGCT AGAGTAAGTA GACGTTGAAA TAGGCGGAGG TAGGTCAGATAATTAACAAC GGCCCTTCGA TCTCATTCAT~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                            Amp 11221 GTTCGCCAGT TAATAGTTTG CGCAACGTTGTTGCCATTGC TACAGGCATC GTGGTGTCAC CAAGCGGTCA ATTATCAAAC GCGTTGCAACAACGGTAACG ATGTCCGTAG CACCACAGTG~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                            Amp 11281 GCTCGTCGTT TGGTATGGCT TCATTCAGCTCCGGTTCCCA ACGATCAAGG CGAGTTACAT CGAGCAGCAA ACCATACCGA AGTAAGTCGAGGCCAAGGGT TGCTAGTTCC GCTCAATGTA~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                            Amp 11341 GATCCCCCAT GTTGTGCAAA AAAGCGGTTAGCTCCTTCGG TCCTCCGATC GTTGTCAGAA CTAGGGGGTA CAACACGTTT TTTCGCCAATCGAGGAAGCC AGGAGGCTAG CAACAGTCTT~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                            Amp 11401 GTAAGTTGGC CGCAGTGTTA TCACTCATGGTTATGGCAGC ACTGCATAAT TCTCTTACTG CATTCAACCG GCGTCACAAT AGTCAGTACCAATACCGTCG TGACGTATTA AGAGAATGAC~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                            Amp 11461 TCATGCCATC CGTAAGATGC TTTTCTGTGACTGGTGAGTA CTCAACCAAG TCATTCTGAG AGTACGGTAG GCATTCTACG AAAAGACACTGACCACTCAT GAGTTGGTTC AGTAAGACTC~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                            Amp 11521 AATAGTGTAT GCGGCGACCG AGTTGCTCTTGCCCGGCGTC AATACGGGAT AATACCGCGC TTATCACATA CGCCGCTGGC TCAACGAGAACGGGCCGCAG TTATGCCCTA TTATGGCGCG~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                            Amp 11581 CACATAGCAG AACTTTAAAA GTGCTCATCATTGGAAAACG TTCTTCGGGG CGAAAACTCT GTGTATCGTC TTGAAATTTT CACGAGTAGTAACCTTTTGC AAGAAGCCCC GCTTTTGAGA~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                            Amp 11641 CAAGGATCTT ACCGCTGTTG AGATCCAGTTCGATGTAACC CACTCGTGCA CCCAACTGAT GTTCCTAGAA TGGCGACAAC TCTAGGTCAAGCTACATTGG GTGAGCACGT GGGTTGACTA~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                            Amp 11701 CTTCAGCATC TTTTACTTTC ACCAGCGTTTCTGGGTGAGC AAAAACAGGA AGGCAAAATG GAAGTCGTAG AAAATGAAAG TGGTCGCAAAGACCCACTCG TTTTTGTCCT TCCGTTTTAC~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                            Amp 11761 CCGCAAAAAA GGGAATAAGG GCGACACGGAAATGTTGAAT ACTCATACTC TTCCTTTTTC GGCGTTTTTT CCCTTATTCC CGCTGTGCCTTTACAACTTA TGAGTATGAG AAGGAAAAAG~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                     Amp                                                  ~~~~~~~~~~                                                      Amp P 11821AATATTATTG AAGCATTTAT CAGGGTTATT GTCTCATGAG CGGATACATA TTTGAATGTATTATAATAAC TTCGTAAATA GTCCCAATAA CAGAGTACTC GCCTATGTAT AAACTTACAT~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                           Amp P 11881 TTTAGAAAAA TAAACAAATA GGGGTTCCGCGCACATTTCC CCGAAAAGTG CCACCTGACG AAATCTTTTT ATTTGTTTAT CCCCAAGGCGCGTGTAAAGG GGCTTTTCAC GGTGGACTGC ~~~~~~~~~~~~~~~~~~~~~~~~~~~          Amp P 11941 TCTAAGAAAC CATTATTATC ATGACATTAA CCTATAAAAATAGGCGTATC ACGAGGCCCT AGATTCTTTG GTAATAATAG TACTGTAATT GGATATTTTTATCCGCATAG TGCTCCGGGA 12001 TTCGTC AAGCAG SEQ ID NO: 29 nucleotidesequence of the suppression expression construct Nat L BB-Opti FEPO inIrwin for feline erythropoietin 1 TCGCGCGTTT CGGTGATGAC GGTGAAAACCTCTGACACAT GCAGCTCCCG GAGACGGTCA AGCGCGCAAA GCCACTACTG CCACTTTTGGAGACTGTGTA CGTCGAGGGC CTCTGCCAGT 61 CAGCTTGTCT GTAAGCGGAT GCCGGGAGCAGACAAGCCCG TCAGGGCGCG TCAGCGGGTG GTCGAACAGA CATTCGCCTA CGGCCCTCGTCTGTTCGGGC AGTCCCGCGC AGTCGCCCAC 121 TTGGCGGGTG TCGGGGCTGG CTTAACTATGCGGCATCAGA GCAGATTGTA CTGAGAGTGC AACCGCCCAC AGCCCCGACC GAATTGATACGCCGTAGTCT CGTCTAACAT GACTCTCACG 181 ACCATATGCC CGTCCGCGTA CCGGCGCGCCGGATGCCAAT CGATGAATTC CGGTGTGAAA TGGTATACGG GCAGGCGCAT GGCCGCGCGGCCTACGGTTA GCTACTTAAG GCCACACTTT 241 TACCGCACAG ATGCGTAAGG AGAAAATACCGCATCAGGCG CCATTCGCCA TTCAGGCTGC ATGGCGTGTC TACGCATTCC TCTTTTATGGCGTAGTCCGC GGTAAGCGGT AAGTCCGACG 301 GCAACTGTTG GGAACGGCGA TCGGTGCGGGCCTCTTCGCT ATTACGCCAG CTGGCGAAAG CGTTGACAAC CCTTCCCGCT AGCCACGCCCGGAGAAGCGA TAATGCGGTC GACCGCTTTC 361 GGGGATGTGC TGCAAGGCGA TTAAGTTGGGTAACGCCAGG GTTTTCCCAG TCACGACGTT CCCCTACACG ACGTTCCGCT AATTCAACCCATTGCGGTCC CAAAAGGGTC AGTGCTGCAA                                                   tRNA                                             ~~~~~~~~~~~~~~~~~~~~                                                    H1                                             ~~~~~~~~~~~~~~~~~~~~ 421GTAAAACGAC GGCCAGTGAA TTGATGCATC CATCAATTCA TATTTGCATG TCGCTATGTGCATTTTGCTG CCGGTCACTT AACTACGTAG GTAGTTAAGT ATAAACGTAC AGCGATACAC                            tRNA~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                             H1~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 481TTCTGGGAAA TCACCATAAA CGTGAAATGT CTTTGGATTT GGGAATCTTA TAAGTTCTGTAAGACCCTTT AGTGGTATTT GCACTTTACA GAAACCTAAA CCCTTAGAAT ATTCAAGACA                            tRNA~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~     H1                             Hyb1 tRNA~~~~~~~~~~~~~~     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 541ATGAGACCAC TCGGATCCGG TGGGGTAGCG AAGTGGCTAA ACGCGGCGGA CTCTAAATCCTACTCTGGTG AGCCTAGGCC ACCCCATCGC TTCACCGATT TGCGCCGCCT GAGATTTAGG               Hyb1 tRNA ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                     tRNA~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                                             Term                                            ~~~~~~ 601 GCTCCCTTTGGGTTCGGCGG TTCGAATCCG TCCCCCACCA TTTTTTGGAA CCTAGGGAAT CGAGGGAAACCCAAGCCGCC AAGCTTAGGC AGGGGGTGGT AAAAAACCTT GGATCCCTTA 661 TCCGGTGTGAAATACCGCAC AGATGCGTAA GGAGAAAATA CCGCATCAGG CGCCATTCGC AGGCCACACTTTATGGCGTG TCTACGCATT CCTCTTTTAT GGCGTAGTCC GCGGTAAGCG 721 CATTCAGGCTGCGCAACTGT TGGGAAGGGC GATCGGTGCG GGCCTCTTCG CTATTACGCC GTAAGTCCGACGCGTTGACA ACCCTTCCCG CTAGCCACGC CCGGAGAAGC GATAATGCGG 781 AGCTGGCGAAAGGGGGATGT GCTGCAAGGC GATTAAGTTG GGTAACGCCA GGGTTTTCCC TCGACCGCTTTCCCCCTACA CGACGTTCCG CTAATTCAAC CCATTGCGGT CCCAAAAGGG                                                           tRNA                                                          ~~~~~~~                                                            H1                                                          ~~~~~~~ 841AGTCACGACG TTGTAAAACG ACGGCCAGTG AATTGATGCA TCCATCAATT CATATTTGCATCAGTGCTGC AACATTTTGC TGCCGGTCAC TTAACTACGT AGGTAGTTAA GTATAAACGT                            tRNA~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                             H1~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 901TGTCGCTATG TGTTCTGGGA AATCACCATA AACGTGAAAT GTCTTTGGAT TTGCGAATCTACAGCGATAC ACAAGACCCT TTAGTGGTAT TTGCACTTTA CAGAAACCTA AACCCTTAGA                            tRNA~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~           H1                              Hyb1 tRNA~~~~~~~~~~~~~~~~~~~~~~~~~~~      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 961TATAAGTTCT GTATGAGACC ACTCGGATCC GGTGGGGTAG CGAAGTGGCT AAACGCGGCGATATTCAAGA CATACTCTGG TGAGCCTAGG CCACCCCATC GCTTCACCGA TTTGCGCCGC                                                          Term                                                         ~~~~~~                           tRNA~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                     Hyb1 tRNA~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 1021GACTCTAAAT CCGCTCCCTT TGGGTTCGGC GGTTCGAATC CGTCCCCCAC CATTTTTTGGCTGAGATTTA GGCGAGGGAA ACCCAAGCCG CCAAGCTTAG GCAGGGGGTG GTAAAAAACC 1081AAGACGTCGA ATTCCGGTGT GAAATACCGC ACAGATGCGT AAGGAGAAAA TACCGCATCATTCTGCAGCT TAAGGCCACA CTTTATGGCG TGTCTACGCA TTCCTCTTTT ATGGCGTAGT 1141GGCGCCATTC GCCATTCAGG CTGCGCAACT GTTGGGAAGG GCGATCGGTG CGGGCCTCTTCCGCGGTAAG CGGTAAGTCC GACGCGTTGA CAACCCTTCC CGCTAGCCAC GCCCGGAGAA 1201CGCTATTACG CCAGCTGGCG AAAGGGGGAT GTGCTGCAAG GCGATTAAGT TGGGTAACGCGCGATAATGC GGTCGACCGC TTTCCCCCTA CACGACGTTC CGCTAATTCA ACCCATTGCG 1261CAGGGTTTTC CCAGTCACGA CGTTGTAAAA CGACGGCCAG TGAATTGATG CATCCATCAAGTCCCAAAAG GGTCAGTGCT GCAACATTTT GCTGCCGGTC ACTTAACTAC GTAGGTAGTT                              tRNA     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                               H1     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 1321TTCATATTTG CATGTCGCTA TGTGTTCTGG GAAATCACCA TAAACGTGAA ATGTCTTTGGAAGTATAAAC GTACAGCGAT ACACAAGACC CTTTAGTGGT ATTTGCACTT TACAGAAACC                            tRNA~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                 H1                               Hyb1 tRNA~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~      ~~~~~~~~~~~~~~~~~~~ 1381ATTTGGGAAT CTTATAAGTT CTGTATGAGA CCACTCGGAT CCGGTGGGGT AGCGAAGTGGTAAACCCTTA GAATATTCAA GACATACTCT GGTGAGCCTA GGCCACCCCA TCGCTTCACC                            tRNA~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                        Hyb1 tRNA~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 1441CTAAACGCGG CGGACTCTAA ATCCGCTCCC TTTGGGTTCG GCGGTTCGAA TCCGTCCCCCGATTTGCGCC GCCTGAGATT TAGGCGAGGG AAACCCAAGC CGCCAAGCTT AGGCAGGGGG     Term     ~~~~~~~    tRNA ~~~~~~~~~~~ Hyb1 tRNA ~~~~ 1501 ACCATTTTTTGGAACATATG GAATTCCGGT GTGAAATACC GCACAGATGC GTAAGGAGAA TGGTAAAAAACCTTGTATAC CTTAAGGCCA CACTTTATGG CGTGTCTACG CATTCCTCTT 1561 AATACCGCATCAGGCGCCAT TCGCCATTCA GGCTGCGCAA CTGTTGGGAA GGGCGATCGG TTATGGCGTAGTCCGCGGTA AGCGGTAAGT CCGACGCGTT GACAACCCTT CCCGCTAGCC 1621 TGCGGGCCTCTTCGCTATTA CGCCAGCTGG CGAAAGGGGG ATGTGCTGCA AGGCGATTAA ACGCCCGGAGAAGCGATAAT GCGGTCGACC GCTTTCCCCC TACACGACGT TCCGCTAATT 1681 GTTGGGTAACGCCAGGGTTT TCCCAGTCAC GACGTTGTAA AACGACGGCC AGTGAATTGA CAACCCATTGCGGTCCCAAA AGGGTCAGTG CTGCAACATT TTGCTGCCGG TCACTTAACT                                     tRNA                  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                                      H1                  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 1741TGCATCCATC AATTCATATT TGCATGTCGC TATGTGTTCT GGGAAATCAC CATAAACGTGACGTAGGTAG TTAAGTATAA ACGTACAGCG ATACACAAGA CCCTTTAGTG GTATTTGCAC                            tRNA~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                      H1                                   Hyb1 tRNA~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~      ~~~~~~ 1801AAATGTCTTT GGATTTGGGA ATCTTATAAG TTCTGTATGA GACCACTCGG ATCCGGTGGGTTTACAGAAA CCTAAACCCT TAGAATATTC AAGACATACT CTGGTGAGCC TAGGCCACCC                            tRNA~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                         Hyb1 tRNA~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 1861GTAGCGAAGT GGCTAAACGC GGCGGACTCT AAATCCGCTC CCTTTGGGTT CGGCGGTTCGCATCGCTTCA CCGATTTGCG CCGCCTGAGA TTTAGGCGAG GGAAACCCAA GCCGCCAAGC                  Term                  ~~~~~~~          tRNA~~~~~~~~~~~~~~~~~~~~~~~~    Hyb1tRNA                                        SVO~~~~~~~~~~~~~~~~~                           ~~~~~~~~~~~~~~~~~~~~~ 1921AATCCGTCCC CCACCATTTT TTGGAACTTA ATTAAGTACG GGCCTCCAAA AAAGCCTCCTTTAGGCAGGG GGTGGTAAAA AACCTTGAAT TAATTCATGC CCGGAGGTTT TTTCGGAGGA                            SVO~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 1981CACTACTTCT GGAATAGCTC AGAGGCAGAG GCGGCCTCGG CCTCTGCATA AATAAAAAAAGTGATGAAGA CCTTATCGAG TCTCCGTCTC CGCCGGAGCC GGAGACGTAT TTATTTTTTT                            SVO~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 2041ATTAGTCAGC CATGGGGCGG AGAATGGGCG GAACTGGGCG GAGTTAGGGG CGGGATGGGCTAATCAGTCG GTACCCCGCC TCTTACCCGC CTTGACCCGC CTCAATCCCC GCCCTACCCG                            SVO~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 2101GGAGTTAGGG GCGGGACTAT GGTTGCTGAC TAATTGAGAT GCATGCTTTG CATACTTCTGCCTCAATCCC CGCCCTGATA CCAACGACTG ATTAACTCTA CGTACGAAAC GTATGAAGAC                            SVO~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 2161CCTGCTGGGG AGCCTGGGGA CTTTCCACAC CTGGTTGCTG ACTAATTGAG ATGCATGCTTGGACGACCCC TCGGACCCCT GAAAGGTGTG GACCAACGAC TGATTAACTC TACGTACGAA     SVO                               CMV~~~~~~~~~~~~~~~     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 2221TGCATACTTC TGCCCGCGGA GTTATTAATA GTAATCAATT ACGGGGTCAT TAGTTCATAGACGTATGAAC ACGGGCGCCT CAATAATTAT CATTAGTTAA TGCCCCAGTA ATCAAGTATC                            CMV~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 2281CCCATATATG GAGTTCCGCG TTACATAACT TACGGTAAAT GGCCCGCCTG GCTGACCGCCGGGTATATAC CTCAAGGCGC AATGTATTGA ATGCCATTTA CCGGGCGGAC CGACTGGCGG                            CMV~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 2341CAACGACCCC CGCCCATTGA CGTCAATAAT GACGTATGTT CCCATAGTAA CGCCAATAGGGTTGCTGGGG GCGGGTAACT GCAGTTATTA CTGCATACAA GGGTATCATT GCGGTTATCC                            CMV~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 2401GACTTTCCAT TGACGTCAAT GGGTGGAGTA TTTACGGTAA ACTGCCCACT TGGCAGTACACTGAAAGGTA ACTGCAGTTA CCCACCTCAT AAATGCCATT TGACGGGTGA ACCGTCATGT                            CMV~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 2461TCAAGTGTAT CATATGCCAA GTACGCCCCC TATTGACGTC AATGACGGTA AATGGCCCGCAGTTCACATA GTATACGGTT CATGCGGGGG ATAACTGCAG TTACTGCCAT TTACCGGGCG                            CMV~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 2521CTGGCATTAT GCCCAGTACA TGACCTTATG GGACTTTCCT ACTTGGCAGT ACATCTACGTGACCGTAATA CGGGTCATGT ACTGGAATAC CCTGAAAGGA TGAACCGTCA TGTAGATGCA                            CMV~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 2581ATTAGTCATC GCTATTACCA TGGTGATGCG GTTTTGGCAG TACATCAATG GGCGTGGATATAATCAGTAG CGATAATGGT ACCACTACGC CAAAACCGTC ATGTAGTTAC CCGCACCTAT                            CMV~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 2641GCGGTTTGAC TCACGGGGAT TTCCAAGCCT CCACCCCATT GACGTCAATG GGAGTTTGTTCGCCAAACTG AGTGCCCCTA AAGGTTCGGA GGTGGGGTAA CTGCAGTTAC CCTCAAACAA                            CMV~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 2701TTGGCACCAA AATCAACGGG ACTTTCCAAA ATGTCGTAAC AACTCCGCCC CATTGACGCAAACCGTGGTT TTAGTTGCCC TGAAAGGTTT TACAGCATTG TTGAGGCGGG GTAACTGCGT                            CMV~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 2761AATGGGCGGT AGGCGTGTAC GGTGGGAGGT CTATATAAGC AGAGCTCTCT GGCTAACTAGTTACCCGCCA TCCGCACATG CCACCCTCCA GATATATTCG TCTCGAGAGA CCGATTGATC              CMV                                   Nat L~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~            ~~~~~~~~~~~~~~~~~~~ 2821AGAACCCACT GCTTACTGGC TTATCGAAAT TACTAGTCCA CCATGGGGTC GTGCGAATGTTCTTGGGTGA CGAATGACCG AATAGCTTTA ATGATCAGGT GGTACCCCAG CACGCTTACA                           Nat L~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 2881CCTGCCCTGC TGCTTCTGCT ATCTTTGCTG CTGCTTCCCC TGGGCCTCCC AGTCCTGGGCGGACGGGACG ACGAAGACGA TAGAAACGAC GACGAAGGGG ACCCGGAGGG TCAGGACCCG                        BB-Opti FEPO~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~AlaProProArg LeuIleCys AspSerArg ValLeuGluArg TyrIleLeu GluAlaArg 2941GCCCCCCCTC GCCTCATCTG TGACAGCCGA GTCCTGGAGA GGTACATTCT GGAGGCCAGGCGGGGGGGAG CGGAGTAGAC ACTGTCGGCT CAGGACCTCT CCATGTAAGA CCTCCGGTCC                        BB-Opti FEPO~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~GluAlaGluAsn ValThrMet GlyCysAla GluGlyCysSer PheSerGlu AsnIleThr 3001GAGGCCGAAA ATGTGACCAT GGGCTGCGCT GAAGGCTGCA GCTTCAGTGA GAATATCACCCTCCGGCTTT TACACTGGTA CCCGACGCGA CTTCCGACGT CGAAGTCACT CTTATAGTGG                        BB-Opti FEPO~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ValProAspThr LysValAsn PheTyrThr TrpLysArgMet AspValGly GlnGlnAla 3061GTTCCGGACA CCAAGGTCAA CTTCTATACC TGGAAGAGGA TGGACGTCGG GCAGCAGGCTCAAGGCCTGT GGTTCCAGTT GAAGATATGG ACCTTCTCCT ACCTGCAGCC CGTCGTCCGA                        BB-Opti FEPO~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ValGluValTrp GlnGlyLeu AlaLeuLeu SerGluAlaIle LeuArgGly GlnAlaLeu 3121GTGGAAGTCT GGCAGGGCCT CGCCCTCCTC AGCGAAGCCA TCCTGCGGGG CCAGGCCCTGCACCTTCAGA CCGTCCCGGA GCGGGAGGAG TCGCTTCGGT AGGACGCCCC GGTCCGGGAC                        BB-Opti FEPO~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~LeuAlaAsnSer SerGlnPro SerGluThr LeuGlnLeuHis ValAspLys AlaValSer 3181CTGGCCAACT CCTCCCAGCC CTCTGAGACC CTGCAGCTGC ATGTCGACAA GGCCGTCAGCGACCGGTTGA GGAGGGTCGG GAGACTCTGG GACGTCGACG TACAGCTGTT CCGGCAGTCG                        BB-Opti FEPO~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~SerLeuArgSer LeuThrSer LeuLeuArg AlaLeuGlyAla GlnLysGlu AlaThrSer 3241AGCCTGCGCA GCCTCACCTC CCTGCTGCGC GCACTGGGAG CCCAGAAGGA AGCCACCTCCTCGGACGCGT CGGAGTGGAG GGACGACGCG CGTGACCCTC GGGTCTTCCT TCGGTGGAGG                        BB-Opti FEPO~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~LeuProGluAla ThrSerAla AlaProLeu ArgThrPheThr ValAspThr LeuCysLys 3301CTTCCCGAGG CAACCTCTGC CGCCCCCTTA AGAACCTTCA CTGTGGACAC TTTGTGCAAGGAAGGGCTCC GTTGGAGACG GCGGGGGAAT TCTTGGAAGT GACACCTGTG AAACACGTTC                        BB-Opti FEPO~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~LeuPheArgIle TyrSerAsn PheLeuArg GlyLysLeuThr LeuTyrThr GlyGluAla 3361CTTTTCCGAA TCTACTCCAA CTTCCTGCGG GGCAAGCTGA CGCTGTACAC AGGGGAGGCCGAAAAGGCTT AGATGAGGTT GAAGGACGCC CCGTTCGACT GCGACATGTG TCCCCTCCGC    BB-Opti FEPO                                    BGH~~~~~~~~~~~~~~~~~~~~~~~                     ~~~~~~~~~~~~~~~~~~~~~CysArgArgGly AspArg*** 3421 TGCCGAAGAG GAGACAGGTG AGCGGCCGCA TCAGCCTCGACTGTGCCTTC TAGTTGCCAG ACGGCTTCTC CTCTGTCCAC TCGCCGGCGT AGTCGGAGCTGACACGGAAG ATCAACGGTC                             BGH~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 3481CCATCTGTTG TTTGCCCCTC CCCCGTGCCT TCCTTGACCC TGGAAGGTGC CACTCCCACTGGTAGACAAC AAACGGGGAG GGGGCACGGA AGGAACTGGG ACCTTCCACG GTGAGGGTGA                            BGH~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 3541GTCCTTTCCT AATAAAATGA GGAAATTGCA TCGCATTGTC TGAGTAGGTG TCATTCTATTCAGGAAAGGA TTATTTTACT CCTTTAACGT AGCGTAACAG ACTCATCCAC AGTAAGATAA                            BGH~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 3601CTGGGGGGTG GGGTGGGGCA GGACAGCAAG GGGGAGGATT GGGAAGACAA TAGCAGGCATGACCCCCCAC CCCACCCCGT CCTGTCGTTC CCCCTCCTAA CCCTTCTGTT ATCGTCCGTA       BGH                                                 Beta~~~~~~~~~~~~~~~~~~                                        ~~~~~~~ 3661GCTGGGGATG CGGTGGGCTC TATGGCTTCT GAGGCGGAAA GAACCAGTGT ACAGCTTTGCCGACCCCTAC GCCACCCGAG ATACCGAAGA CTCCGCCTTT CTTGGTCACA TGTCGAAACG                            Beta~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 3721TTCTCAATTT CTTATTTGCA TAATGAGAAA AAAAGGAAAA TTAATTTTAA CACCAATTCAAAGAGTTAAA GAATAAACGT ATTACTCTTT TTTTCCTTTT AATTAAAATT GTGGTTAAGT                            Beta~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 3781GTAGTTGATT GAGCAAATGC GTTGCCAAAA AGGATGCTTT AGAGACAGTG TTCTCTGCACCATCAACTAA CTCGTTTACG CAACGGTTTT TCCTACGAAA TCTCTGTCAC AAGAGACGTG                            Beta~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 3841AGATAAGGAC AAACATTATT CAGAGGGAGT ACCCAGAGCT GAGACTCCTA AGCCAGTGAGTCTATTCCTG TTTGTAATAA GTCTCCCTCA TGCGTCTCGA CTCTGAGGAT TCGGTCACTC                            Beta~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 3901TGGCACAGCA TCCAGGGAGA AATATGCTTG TCATCACCGA AGCCTGATTC CGTAGAGCCAACCGTGTCGT AGGTCCCTCT TTATACGAAC AGTAGTGGCT TCGGACTAAG GCATCTCGGT                            Beta~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 3961CACCCTGGTA AGGGCCAATC TGCTCACACA GGATAGAGAG GGCAGGAGCC AGGGCAGAGCGTGGGACCAT TCCCGGTTAG ACGAGTGTGT CCTATCTCTC CCGTCCTCGG TCCCGTCTCG                            Beta~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 4021ATATAAGGTG AGGTAGGATC AGTTGCTCCT CACATTTGCT TCTGACATAG TTGTGTTGGGTATATTCCAC TCCATCCTAG TCAACGAGGA GTGTAAACGA AGACTGTATC AACACAACCC 4081AGCTTGGATA GCTTGGGGGG GGGACAGCTC AGGGCTGCGA TTTCGCGCCA ACTTGACGGCTCGAACCTAT CGAACCCCCC CCCTGTCGAG TCCCGACGCT AAAGCGCGGT TGAACTGCCG                                                   OptEcAFRS                                                ~~~~~~~~~~~~~~~~~ 4141AATCCTAGCG TGAAGGCTGG TAGGATTTTA TCCCTCGAGC CACCATGGCC TCCAGCAACCTTAGGATCGC ACTTCCGACC ATCCTAAAAT AGGGAGCTCG GTGGTACCGG AGGTCGTTGG                         OptEcAFRS~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 4201TGATCAAGCA GCTCCAGGAG AGGGGCCTCG TGGCTCAGGT CACCGACGAA GAAGCACTCGACTAGTTCGT CGAGGTCCTC TCCCCGGAGC ACCGAGTCCA GTGGCTGCTT CTTCGTGAGC                         OptEcAFRS~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 4261CTGAAAGACT GGCCCAGGGA CCCATTGCAC TGATCTGCGG GTTCGATCCT ACAGCCGACTGACTTTCTGA CCGGGTCCCT GGGTAACGTG ACTAGACGCC CAAGCTAGGA TGTCGGCTGA                         OptEcAFRS~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 4321CTCTCCACCT GGGTCATCTC GTGCCACTGC TGTGTCTCAA ACGGTTTCAG CAGGCTGGCCGAGAGGTGGA CCCAGTAGAG CACGGTGACG ACACAGAGTT TGCCAAAGTC GTCCGACCGG                         OptEcAFRS~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 4381ACAAGCCCGT CGCACTGGTG GGAGGTGCTA CTGGGCTGAT TGGCGATCCT AGTTTCAAAGTGTTCGGGCA GCGTGACCAC CCTCCACGAT GACCCGACTA ACCGCTAGGA TCAAAGTTTC                         OptEcAFRS~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 4441CCGCAGAGCG CAAGCTCAAT ACCGAGGAGA CAGTGCAGGA ATGGGTCGAC AAAATCCGAAGGCGTCTCGC GTTCGAGTTA TGGCTCCTCT GTCACGTCCT TACCCAGCTG TTTTAGGCTT                         OptEcAFRS~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 4501AGCAGGTCGC CCCATTTCTG GATTTCGACT GCGGAGAGAA CTCAGCTATT GCCGCAAATATCGTCCAGCG GGGTAAAGAC CTAAAGCTGA CGCCTCTCTT GAGTCGATAA CGGCGTTTAT                         OptEcAFRS~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 4561ACTACGATTG GTTTGGGAAT ATGAACGTCC TCACTTTCCT GCGTGACATC GGTAAACATTTGATGCTAAC CAAACCCTTA TACTTGCAGG AGTGAAAGGA CGCACTGTAG CCATTTGTAA                         OptEcAFRS~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 4621TTTCCGTGAA TCAGATGATT AACAAGGAAG CTGTGAAGCA GAGGCTGAAT AGAGAGGGCCAAAGGCACTT AGTCTACTAA TTGTTCCTTC GACACTTCGT CTCCGACTTA TCTCTCCCGG                         OptEcAFRS~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 4681AGGGAATCAG CTTCACCGAA TTTTCTTATA ATCTCCTGCA GGGGTACGGT ATGGCCTGTGTCCCTTAGTC GAAGTGGCTT AAAAGAATAT TAGAGGACGT CCCCATGCCA TACCGGACAC                         OptEcAFRS~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 4741CAAACAAACA GTATGGCGTC GTGCTGCAGA TTGGAGGCAG TGATCAGTGG GGGAACATCAGTTTGTTTGT CATACCGCAG CACGACGTCT AACCTCCGTC ACTAGTCACC CCCTTGTAGT                         OptEcAFRS~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 4801CATCAGGTAT TGACCTCACT CGGCGCCTGC ACCAGAATCA GGTCTTTGGA CTCACCGTGCGTAGTCCATA ACTGGAGTGA GCCGCGGACG TGGTCTTAGT CCAGAAACCT GAGTGGCACG                         OptEcAFRS~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 4861CCCTGATCAC AAAGGCTGAT GGCACAAAAT TTGGTAAGAC CGAGGGTGGA GCCGTGTGGCGGGACTAGTG TTTCCGACTA CCGTGTTTTA AACCATTCTG GCTCCCACCT CGGCACACCG                         OptEcAFRS~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 4921TGGACCCTAA AAAGACATCC CCATACAAAT TCTATCAGTT TTGGATCAAC ACTGCAGATGACCTGGGATT TTTCTGTAGG GGTATGTTTA AGATAGTCAA AACCTAGTTG TGACGTCTAC                         OptEcAFRS~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 4981CTGACGTCTA CCGATTCCTC AAGTTTTTCA CCTTTATGAG CATTGAGGAA ATCAATGCCCGACTGCAGAT GGCTAAGGAG TTCAAAAAGT GGAAATACTC GTAACTCCTT TAGTTACGGG                         OptEcAFRS~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 5041TGGAGGAAGA GGATAAGAAC TCTGGCAAAG CTCCCCGTGC ACAGTATGTG CTCGCCGAACACCTCCTTCT CCTATTCTTG AGACCGTTTC GAGGGGCACG TGTCATACAC GAGCGGCTTG                         OptEcAFRS~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 5101AGGTCACAAG GCTGGTGCAT GGGGAGGAAG GTCTGCAGGC TGCCAAGAGA ATTACTGAGTTCCAGTGTTC CGACCACGTA CCCCTCCTTC CAGACGTCCG ACGGTTCTCT TAATGACTCA                         OptEcAFRS~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 5161GCCTCTTCAG TGGCTCACTG TCCGCACTGA GCGAAGCTGA CTTTGAGCAG CTCGCCCAGGCGGAGAAGTC ACCGAGTGAC AGGCGTGACT CGCTTCGACT GAAACTCGTC CAGCGGGTCC                         OptEcAFRS~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 5221ATGGAGTGCC TATGGTCGAG ATGGAAAAAG GCGCAGACCT GATGCAGGCT CTCGTGGATTTACCTCACGG ATACCAGCTC TACCTTTTTC CGCGTCTGGA CTACGTCCGA GAGCACCTAA                         OptEcAFRS~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 5281CTGAGCTGCA GCCAAGTCGG GGGCAGGCCC GCAAGACCAT CGCATCAAAT GCTATTACAAGACTCGACGT CGGTTCAGCC CCCGTCCGGG CGTTCTGGTA GCGTAGTTTA CGATAATGTT                         OptEcAFRS~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 5341TCAACGGTGA AAAACAGTCC GACCCCGAGT ACTTCTTTAA GGAAGAGGAT CGACTGTTCGAGTTGCCACT TTTTGTCAGG CTGGGGCTCA TGAAGAAATT CCTTCTCCTA GCTGACAAGC                         OptEcAFRS~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 5401GACGTTTTAC CCTCCTGAGG AGAGGCAAAA AGAATTATTG TCTGATTTGC TGGAAGTGATCTGCAAAATG GGAGGACTCC TCTCCGTTTT TCTTAATAAC AGACTAAACG ACCTTCACTA                              IRES     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 5461CTAGAGGCCG CGCAGTTAAC GCCGCCCCTC TCCCTCCCCC CCCCTAACGT TACTGGCCGAGATCTCCGGC GCGTCAATTG CGGCGGGGAG AGGGAGGGGG GGGGATTGCA ATGACCGGCT                           IRES~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 5521AGCCGCTTGG AATAAGGCCG GTGTGCGTTT GTCTATATGT TATATTCCAC CATATTGCCGTCGGCGAACC TTATTCCGGC CACACGCAAA CAGATATACA ATATAAGGTG GTATAACGGC                           IRES~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 5581TCTATTGGCA ATGTGAGGGC CCGGAAACCT GGCCCTGTCT TCTTGACGAG CATTCCTAGGAGATAACCGT TACACTCCCG GGCCTTTGGA CCGGGACAGA AGAACTGCTC GTAAGGATCC                           IRES~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 5641GGTCTTTCCC CTCTCGCCAA AGGAATGCAA GGTCTGTTGA ATGTCGTGAA GGAAGCAGTTCCAGAAAGGG GAGAGCGGTT TCCTTACGTT CCAGACAACT TACAGCACTT CCTTCGTCAA                            IRES~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 5701CCTCTGGAAG CTTCTTGAAG ACAAACAACG TCTGTAGCGA CCCTTTGCAG GCAGCGGAACGGAGACCTTC GAAGAACTTC TGTTTGTTGC AGACATCGCT GGGAAACGTC CGTCGCCTTG                            IRES~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 5761CCCCCACCTG GCGACAGGTG CCTCTGCGGC CAAAAGCCAC GTGTATAAAA TACACCTGCAGGGGGTGGAC CGCTGTCCAC GGAGACGCCG GTTTTCGGTG CACATATTTT ATGTGGACGT                            IRES~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 5821AAGGCGGCAC AACCCCAGTG CGACGTTGTG AGTTGGATAG TTGTGGAAAG AGTCAAATGGTTCCGCCGTG TTGGGGTCAC GCTGCAACAC TCAACCTATC AACACCTTTC TCAGTTTACC                            IRES~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 5881CTCTCCTCAA GCGTATTCAA CAAGGGGCTG AAGGATGCCC AGAAGGTACC CCATTGTATGGAGAGGAGTT CGCATAAGTT GTTCCCCGAC TTCCTACGGG TCTTCCATGG GGTAACATAC                            IRES~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 5941GGATCTGATC TGGGGCCTCG GTACACATGC TTTACATGTG TTTAGTCGAG GTTAAAAAAACCTAGACTAG ACCCCGGAGC CATGTGTACG AAATGTACAC AAATCAGCTC CAATTTTTTT                            IRES~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 6001CGTCTAGGCC CCCCGAACCA CGGGGACGTG GTATTCCTTT GAAAAACACG ATGATAATATGCAGATCCGG GGGGCTTGGT GCCCCTGCAC CATAAGGAAA CTTTTTGTGC TACTATTATA IRES                                           DHFR~~~~~~~                              ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 6061GGCCACACCC GTCCGAGATC ACCCTCGAGC CACCATGGTT CGACCATTGA ACTGCATCGTCCGGTGTGGG CAGGCTCTAG TGGGAGCTCG GTGGTACCAA GCTGGTAACT TGACGTAGCA                            DHFR~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 6121CGCCGTGTCC CAAAATATGG GGATTGGCAA GAACGGAGAC CTACCCTGGC CTCCGCTCAGGCGGCACAGG GTTTTATACC CCTAACCGTT CTTGCCTCTG GATGGGACCG GAGGCGAGTC                            DHFR~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 6181GAACGAGTTC AAGTACTTCC AAAGAATGAC CACAACCTCT TCAGTGGAAG GTAAACAGAACTTGCTCAAG TTCATGAAGG TTTCTTACTG GTGTTGGAGA AGTCACCTTC CATTTGTCTT                            DHFR~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 6241TCTGGTGATT ATGGGTAGGA AAACCTGGTT CTCCATTCCT GAGAAGAATC GACCTTTAAAAGACCACTAA TACCCATCCT TTTGGACCAA GAGGTAAGGA CTCTTCTTAG CTGGAAATTT                            DHFR~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 6301GGACAGAATT AATATAGTTC TCAGTAGAGA ACTCAAAGAA CCACCACGAG GAGCTCATTTCCTGTCTTAA TTATATCAAG AGTCATCTCT TGAGTTTCTT GGTGGTGCTC CTCGAGTAAA                            DHFR~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 6361TCTTGCCAAA AGTTTGGATG ATGCCTTAAG ACTTATTGAA CAACCGGAAT TGGCAAGTAAAGAACGGTTT TCAAACCTAC TACGGAATTC TGAATAACTT GTTGGCCTTA ACCGTTCATT                            DHFR~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 6421AGTAGACATG GTTTGGATAG TCGGAGGCAG TTCTGTTTAC CAGGAAGCCA TGAATCAACCTCATCTGTAC CAAACCTATC AGCCTCCGTC AAGACAAATG GTCCTTCGGT ACTTAGTTGG                            DHFR~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 6481AGGCCACCTC AGACTCTTTG TGACAAGGAT CATGCAGGAA TTTGAAAGTG ACACGTTTTTTCCGGTGGAG TCTGAGAAAC ACTGTTCCTA GTACGTCCTT AAACTTTCAC TGTGCAAAAA                            DHFR~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 6541CCCAGAAATT GATTTGGGGA AATATAAACT TCTCCCAGAA TACCCAGGCG TCCTCTCTGAGGGTCTTTAA CTAAACCCCT TTATATTTGA AGAGGGTCTT ATGGGTCCGC AGGAGAGACT                          DHFR~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 6601GGTCCAGGAG GAAAAAGGCA TCAAGTATAA GTTTGAAGTC TACGAGAAGA AAGACTAATCCCAGGTCCTC CTTTTTCCGT AGTTCATATT CAAACTTCAG ATGCTCTTCT TTCTGATTAG 6661TAGAGCCAGA TCTCCAATTG CACGGGCTAC GAGATTTCGA TTCCACCGCC GCCTTCTATGATCTCGGTCT AGAGGTTAAC GTGCCCGATG CTCTAAAGCT AAGGTGGCGG CGGAAGATAC 6721AAAGGTTGGG CTTCGGAATC GTTTTCCGGG ACGCCGGCTG GATGATCCTC CAGCGCGGGGTTTCCAACCC GAAGCCTTAG CAAAAGGCCC TGCGGCCGAC CTACTAGGAG GTCGCGCCCC                                        SV40 PolyA                               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 6781ATCTCATGCT GGAGTTCTTC GCCCACCCCA ACTTGTTTAT TGCAGCTTAT AATGGTTACATAGAGTACGA CCTCAAGAAG CGGGTGGGGT TGAACAAATA ACGTCGAATA TTACCAATGT                         SV40 PolyA~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 6841AATAAAGCAA TAGCATCACA AATTTCACAA ATAAAGCATT TTTTTCACTG CATTCTAGTTTTATTTCGTT ATCGTAGTGT TTAAAGTGTT TATTTCGTAA AAAAAGTGAC GTAAGATCAA              SV40 PolyA ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 6901GTGGTTTGTC CAAACTCATC AATGTATCTT ATCATGTCGG TTACCCCCGT CCGACATGTGCACCAAACAG GTTTGAGTAG TTACATAGAA TAGTACAGCC AATGGGGGCA GGCTGTACAC                                                            pUC Ori 6961AGCAAAAGGC CAGCAAAAGG CCAGGAACCG TAAAAAGGCC GCGTTGCTGG CGTTTTTCCATCGTTTTCCG GTCGTTTTCC GGTCCTTGGC ATTTTTCCGG CGCAACGACC GCAAAAAGGT~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                          pUC Ori 7021 TAGGCTCCGC CCCCCTGACG AGCATCACAAAAATCGACGC TCAAGTCAGA GGTGGCGAAA ATCCGAGGCG GGGGGACTGC TCGTAGTGTTTTTAGCTGCG AGTTCAGTCT CCACCGCTTT~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                          pUC Ori 7081 CCCGACAGGA CTATAAAGAT ACCAGGCGTTTCCCCCTGGA AGCTCCCTCG TGCGCTCTCC GGGCTGTCCT GATATTTCTA TGGTCCGCAAAGGGGGACCT TCGAGGGAGC ACGCGAGAGG~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                          pUC Ori 7141 TGTTCCGACC CTGCCGCTTA CCGGATACCTGTCCGCCTTT CTCCCTTCGG GAAGCGTGGC ACAAGGCTGG GACGGCGAAT GGCCTATGGACAGGCGGAAA GAGGGAAGCC CTTCGCACCG~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                          pUC Ori 7201 GCTTTCTCAT AGCTCACGCT GTAGGTATCTCAGTTCGGTG TAGGTCGTTC GCTCCAAGCT CGAAAGAGTA TCGAGTGCGA CATCCATAGAGTCAAGCCAC ATCCAGCAAG CGAGGTTCGA~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                          pUC Ori 7261 GGGCTGTGTG CACGAACCCC CCGTTCAGCCCGACCGCTGC GCCTTATCCG GTAACTATCG CCCGACACAC GTGCTTGGGG GGCAAGTCGGGCTGGCGACG CGGAATAGGC CATTGATAGC~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                          pUC Ori 7321 TCTTGAGTCC AACCCGGTAA GACACGACTTATCGCCACTG GCAGCAGCCA CTGGTAACAG AGAACTCAGG TTGGGCCATT CTGTGCTGAATAGCGGTGAC CGTCGTCGGT GACCATTGTC~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                          pUC Ori 7381 GATTAGCAGA GCGAGGTATG TAGGCGGTGCTACAGAGTTC TTGAAGTGGT GGCCTAACTA CTAATCGTCT CGCTCCATAC ATCCGCGACGATGTCTCAAG AACTTCACCA CCGGATTGAT~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                          pUC Ori 7441 CGGCTACACT AGAAGAACAG TATTTGGTATCTGCGCTCTG CTGAAGCCAG TTACCTTCGG GCCGATGTGA TCTTCTTGTC ATAAACCATAGACGCGAGAC GACTTCGGTC AATGGAAGCC~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                          pUC Ori 7501 AAAAAGAGTT GGTAGCTCTT GATCCGGCAAACAAACCACC GCTGGTAGCG GTGGTTTTTT TTTTTCTCAA CCATCGAGAA CTAGGCCGTTTGTTTGGTGG CGACCATCGC CACCAAAAAA~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                          pUC Ori 7561 TGTTTGCAAG CAGCAGATTA CGCGCAGAAAAAAAGGATCT CAAGAAGATC CTTTGATCTT ACAAACGTTC GTCGTCTAAT GCGCGTCTTTTTTTCCTAGA GTTCTTCTAG GAAACTAGAA~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                          pUC Ori 7621 TTCTACGGGG TCTGACGCTC AGTGGAACGAAAACTCACGT TAAGGGATTT TGGTCATGAG AAGATGCCCC AGACTGCGAG TCACCTTGCTTTTGAGTGCA ATTCCCTAAA ACCAGTACTC ~~~~~~~~~  pUC Ori 7681 ATTATCAAAAAGGATCTTCA CCTAGATCCT TTTAAATTAA AAATGAAGTT TTAAATCAAT TAATAGTTTTTCCTAGAAGT GGATCTAGGA AAATTTAATT TTTACTTCAA AATTTAGTTA 7741 CTAAAGTATATATGAGTAAA CTTGGTCTGA CAGTTACCAA TGCTTAATCA GTGAGGCACC GATTTCATATATACTCATTT GAACCAGACT GTCAATGGTT ACGAATTAGT CACTCCGTGG                                    ~~~~~~~~~~~~~~~~~~~~~~~~~~                                                Amp 7801 TATCTCAGCGATCTGTCTAT TTCGTTCATC CATAGTTGCC TGACTCCCCG TCGTGTAGAT ATAGAGTCGCTAGACAGATA AAGCAAGTAG GTATCAACGG ACTGAGGGGC AGCACATCTA~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                            Amp 7861 AACTACGATA CGGGAGGGCT TACCATCTGGCCCCAGTGCT GCAATGATAC CGCGAGACCC TTGATGCTAT GCCCTCCCGA ATGGTAGACCGGGGTCACGA CGTTACTATG GCGCTCTGGG~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                            Amp 7921 ACGCTCACCG GCTCCAGATT TATCAGCAATAAACCAGCCA GCCGGAAGGG CCGAGCGCAG TGCGAGTGGC CGAGGTCTAA ATAGTCGTTATTTGGTCGGT CGGCCTTCCC GGCTCGCGTC~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                            Amp 7981 AAGTGGTCCT GCAACTTTAT CCGCCTCCATCCAGTCTATT AATTGTTGCC GGGAAGCTAG TTCACCAGGA CGTTGAAATA GGCGGAGGTAGGTCAGATAA TTAACAACGG CCCTTCGATC~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                            Amp 8041 AGTAAGTAGT TCGCCAGTTA ATAGTTTGCGCAACGTTGTT GCCATTGCTA CAGGCATCGT TCATTCATCA AGCGGTCAAT TATCAAACGCGTTGCAACAA CGGTAACGAT GTCCGTAGCA~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                            Amp 8101 GGTGTCACGC TCGTCGTTTG GTATGGCTTCATTCAGCTCC GGTTCCCAAC GATCAAGGCG CCACAGTGCG AGCAGCAAAC CATACCGAAGTAAGTCGAGG CCAAGGGTTG CTAGTTCCGC~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                            Amp 8161 AGTTACATGA TCCCCCATGT TGTGCAAAAAAGCGGTTAGC TCCTTCGGTC CTCCGATCGT TCAATGTACT AGGGGGTACA ACACGTTTTTTCGCCAATCG AGGAAGCCAG GAGGCTAGCA~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                            Amp 8221 TGTCAGAAGT AAGTTGGCCG CAGTGTTATCACTCATGGTT ATGGCAGCAC TGCATAATTC ACAGTCTTCA TTCAACCGGC GTCACAATAGTGAGTACCAA TACCGTCGTG ACGTATTAAG~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                            Amp 8281 TCTTACTGTC ATGCCATCCG TAAGATGCTTTTCTGTGACT GGTGAGTACT CAACCAAGTC AGAATGACAG TACGGTAGGC ATTCTACGAAAAGACACTGA CCACTCATGA GTTGGTTCAG~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                            Amp 8341 ATTCTGAGAA TAGTGTATGC GGCGACCGAGTTGCTCTTGC CCGGCGTCAA TACGGGATAA TAAGACTCTT ATCACATACG CCGCTGGCTCAACGAGAACG GGCCGCAGTT ATGCCCTATT~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                            Amp 8401 TACCGCGCCA CATAGCAGAA CTTTAAAAGTGCTCATCATT GGAAAACGTT CTTCGGGGCG ATGGCGCGGT GTATCGTCTT GAAATTTTCACGAGTAGTAA CCTTTTGCAA GAAGCCCCGC~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                            Amp 8461 AAAACTCTCA AGGATCTTAC CGCTGTTGAGATCCAGTTCG ATGTAACCCA CTCGTGCACC TTTTGAGAGT TCCTAGAATG GCGACAACTCTAGGTCAAGC TACATTGGGT GAGCACGTGG~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                            Amp 8521 CAACTGATCT TCAGCATCTT TTACTTTCACCAGCGTTTCT GGGTGAGCAA AAACAGGAAG GTTGACTAGA AGTCGTAGAA AATGAAAGTGGTCGCAAAGA CCCACTCGTT TTTGTCCTTC~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                            Amp 8581 GCAAAATGCC GCAAAAAAGG GAATAAGGGCGACACGGAAA TGTTGAATAC TCATACTCTT CGTTTTACGG CGTTTTTTCC CTTATTCCCGCTGTGCCTTT ACAACTTATG AGTATGAGAA~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                         Amp                                                            ~                                                            Amp P 8641CCTTTTTCAA TATTATTGAA GCATTTATCA GGGTTATTGT CTCATGAGCG GATACATATTGGAAAAAGTT ATAATAACTT CGTAAATAGT CCCAATAACA GAGTACTCGC CTATGTATAA~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                           Amp P 8701 TGAATGTATT TAGAAAAATA AACAAATAGGGGTTCCGCGC ACATTTCCCC GAAAAGTGCC ACTTACATAA ATCTTTTTAT TTGTTTATCCCCAAGGCGCG TGTAAAGGGG CTTTTCACGG ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~              Amp P 8761 ACCTGACGTC TAAGAAACCA TTATTATCAT GACATTAACCTATAAAAATA GGCGTATCAC TGGACTGCAG ATTCTTTGGT AATAATAGTA CTGTAATTGGATATTTTTAT CCGCATAGTG 8821 GAGGCCCTTT CGTC CTCCGGGAAA GCAG

The transformation of E. coli with plasmids containing the modified fEPOgene and the orthogonal aminoacyl tRNA synthetase/tRNA pair (specificfor the desired non-naturally encoded amino acid) allows thesite-specific incorporation of non-naturally encoded amino acid into thefEPO polypeptide. The transformed E. coli, grown at 37° C. in mediacontaining between 0.01-100 mM of the particular non-naturally encodedamino acid, expresses modified fEPO with high fidelity and efficiency.The His-tagged fEPO containing a non-naturally encoded amino acid isproduced by the E. coli host cells as inclusion bodies or aggregates.The aggregates are solubilized and affinity purified under denaturingconditions in 6M guanidine HCl. Refolding is performed by dialysis at 4°C. overnight in 50 mM TRIS-HCl, pH8.0, 40 μM CuSO₄, and 2% (w/v)Sarkosyl. The material is then dialyzed against 20 mM TRIS-HCl, pH 8.0,100 mM NaCl, 2 mM CaCl₂, followed by removal of the His-tag. See Boisselet al., (1993) 268:15983-93. Methods for purification of fEPO are wellknown in the art (Nahri et al., (1991) JBC, Vol 266, pp 23022-23026;Narhi et al., (2001) Protein Engineering, Vol 14, pp 135-140; Darling etal., (2002) Biochemistry Vol 41, pp 14524-14531; Boissel et al., (1993)268:15983-93; and WO0032772A2) and are confirmed by SDS-PAGE, WesternBlot analyses, or electrospray-ionization ion trap mass spectrometry.

Example 3

A suppression expression DNA expression vector was constructed accordingto the invention, expressing feline erythropoietin protein (fEPO).

A. Expression Vector Construction

The expression construct, depicted in FIG. 25, comprises eight copies ofa hybrid tRNA gene encoding an tRNA transcript capable of being chargewith p-acetylphenylalanine by it's cognate tRNA synthetase. Each copy ofthe tRNA gene includes a H1 promoter region, the tRNA sequence and apolymerase III transcription termination signal.

Following the tRNA genes is located a Simian virus SV40 origin ofreplication (SVO), which facilitates replication of the expressionconstruct (vector) in COS cells following transient transfection.

Thereafter is located an expression cassette for the gene sequences ofinterest, which in this case is the feline EPO coding region. First inthe cassette is the human cytomegalovirus promoter (CMV), which drivesexpression of the message. The message in this construct encodes thefeline erythropoietin (fEPO), which is sequentially preceded by thenatural signal peptide (Nat L). The message is followed by the bovinegrowth hormone polyadenylation signal (BGH).

Thereafter is situated an expression cassette beginning with the mousebeta-globulin major promoter (beta), situated within the cassette so asto drive the expression of sequences encoding the optimized E. coliacetylphenylalanine tRNA synthetase (OptEcAFRS), the murinedihydrofolate reductase (DHFR) and the salmonella neomycinphosphotransferase gene (Neo) each separated by an internal ribosomeentry site (IRES) derived from the Encephalomyocarditis virus geneome.The Neo sequence is followed by the SV40 early polyadenylation signal(SV).

The vector also contains sequences required for replication in bacteria,including the colE1 origin (pUC Ori) of replication and thebeta-lactamase gene to confer ampicillin resistance (Amp).

The EMCV is commercially available, cDNA was commercially synthesized tothe IRES region within the viral genome. PCR (polymerase chain reaction)amplification of that cDNA was performed in order to amplify the DNA, aswell as to add 5′ and 3′ ends suitable for insertion between the codingdomains. The ATG trinucleotide at position 834-836 (Genbank accessionnumber NC-001479) was used as the start codon for the DHFR and Neosequences.

Because the literature indicates that translation of the open readingframe downstream of the IRES would be less efficient than the upstreamopen reading frame (translation initiated by 5′ CAP), the strategy wastaken to place the DHFR and Neo genes following independent IRESelements to selectively impair said dominant selectable markers in aneffort to ease clone selection.

Two versions of the suppression expression vector were generated anddesignated Lucy F (FIG. 25) and Irwin (FIG. 26). Lucy F contains 8copies of the tRNA genes, a second IRES, and the Neo gene. The Neo geneis included to allow for selection of stable integrated plasmids intothe cell genome via treatment with G418. Irwin by contrast contains only4 copies of the tRNA genes and lacks the second IRES and Neo. Irwin isthereby smaller in size and better suited for transient expression ofsuppressed proteins for generation of experimental levels of proteinproduction.

B. CHO Cell Expression

The vector “Nat L BB-Opti FEPO in Irwin”, a map of which is depicted inFIG. 28, and the sequence of which is set forth in Table 3 containingthe suppression elements and encoding the feline EPO protein wastransfected into CHO-S cells using a transient transfection protocol.These transfections were performed in parallel with wild type and 22variants of fEPO such that amber codons were placed within the codingregion subject to suppression in a manner so as to retain fEPObioactivity and glycan structure. The 22 variants of fEPO include thoseshown in FIG. 30: K52, Q86, E89, E31, E21, E37, R131, K116, F133, L130,R53, Y49, T132, A1, S120, R76, P129, S36, D55, A128, E72, R163.Experimental results indicate the wild type sequence expresses well andthat suppression expression of the 22 different variants varied widely,but at least 19 of the 22 demonstrated expression as detectable byELISA. Accordingly, an embodiment of the inventive suppressionexpression construct is expected to express gene sequences of interestwith amber suppression codons located at a variety of positions.

Transient expression of fEPO may be used to accommodate some technicalchallenges in producing this protein e.g. having an isoelectric pointaround pH 4 and the high glycosylation of fEPO (over 40% of the mass)which can affect conjugation efficiency and some site accessibility,therefore alternate chemistries may be used as well as alternateexpression systems.

Example 4 Generation of G418 Resistant Cell Lines

The suppression expression construct in this example encodes themodified feline EPO protein with the amber codon positioned at residue 1replacing the nothial alanine residue. This expression construct isreferred to as “Nat L BB-Opti FEPO in Lucy F”, a map of which isdepicted in FIG. 3, and the sequence of which is set forth in FIG. 4.

Nat L BB-Opti FEPO A1 in Lucy F (containing the amber codon at positionA1) was transfected into the CHO-DG44 parent cell line. Transfectionswere performed using 0.5, 1.0, or 2.0 ug linearized DNA per4.times.10.sup.6 CHO cells per 96 well plate. Dominant selection ofstably transfected cells was accomplished via the expression constructencoded neomycin resistance marker and media (CHO-S-SFM II+HT)containing G418.

Viable wells were identified, expanded to small scale (50 ml) shakerculture and cellular productivity assessed by ELISA assay. A variety ofG418 resistant cell isolates were obtained producing easily detectablesecreted fEPO. Two in particular, 5B5 and 15B3 were determined to beproducing 0.07 and 0.1 mg/L in 3-4 days respectively, or 0.03picogram/cell/day (pcd). Secreted fEPO was detected by ELISA as usingthe StemCell EPO ELISA KIT-Immunoassy for Human Erythropoietin, cat#01630.

Example 5 A. Increases in Expression via Genomic Amplification

The Lucy F suppression expression system contains an expression cassetteencoding the murine DHFR gene. As the parent CHO-DG44 cell line used forexpression is completely deficient in DHFR enzymatic activity (doubledeletion), amplification of the integrated target gene (murine DHFR) ispossible by growth selection in media containing methotrexate (MTX).During this amplification, the directly linked protein gene (in thisexample fEPO) is concomitantly amplified. Thus it is possible to isolatecell lines producing elevated amounts of fEPO. Our first round selectionof G418 resistant cell lines is performed in 5 nM MTX. Highest levelproducers (as determined by ELISA) are then identified andcharacterized.

The fEPO G418 resistant cell lineages 5B5 and 15B3 were subjected to 5nM MTX amplification. In each case the suppression expression levels areelevated following amplification and are listed below.

TABLE 4 G418 G418 5 nM MTX 5 nM MTX Fold pg/cell/ mg/L/3- pg/cell/mg/L/3- increase in Cell Line day 4 days day 4 days pg/cell/day 5B5 0.030.07 — — 5B5-8C9 0.03 0.07 0.14 0.41 4.7 15B3 0.03 0.10 — — 15B3-7E30.03 0.10 0.10 0.22 3.3

As can be seen from the above table, expression levels at 5 nM MTXamplification are elevated roughly 3-5 fold. Subsequent amplificationsat increasing concentrations of MTX are expected to yield furtherincrease in productivity.

Example 6

Twenty-two fEPO variants were transiently expressed in Chinese hamsterovary cells (CHOs). The variants of fEPO were constructed intoexpression vector, which contains tRNA and RS. Wild type of fEPO wasconstructed into another expression vector, which doesn't contain IRNAand RS. Plasmids (variants and w.t. fEPO) were transfected into CHOcells with or without pAF using transfection method developed bycompany.

Method of Transient Expression of w.t. fEPO and Variants of fEPO

A solution of polyethyleimine (PEI), a 25 kDa linear from Polysciences,was prepared at 1 mg/ml in distilled water, the pH was adjusted to 7.2and filter sterilized using a 0.22 μm filter before use.

CHO cells (Invitrogen) were maintained in CHO FreeStyle media withglutamine supplemented. A 30 mL culture was prepared in 125 mlErlenmeyer flask from Corning. Cells were seeded at 0.5×6/ml day beforetransfection. Cell density was adjusted to 1×10⁶/mL with growth mediumbefore transfection. Para-acetyl-phenylalanine was added in aconcentration of 1 mM before transfection. DNA, 37 μg of DNA, wasdissolved in RPMI medium and then 74 μL of 1 mg/mL PEI solution wasadded into RPMI media containing DNA. This was incubated for 15 minutes.Then DNA and PEI mixture were added into 30 ml culture in 125 mlErlenmeyer flask. The flask was then transferred to 37° C. incubatorafter which the supernatant was quantified by human ELISA assay 72 hrsafter transfection. FIG. 30 shows the suppression levels of fEPOvariants in the presence of pAF.

Each variant of fEPO was suppressed at different levels, modulated bythe position of pAF. K52, Q86, and E89 were not detected by ELISA assayin the presence of pAF. Without pAF, the variants of fEPO weren'tdetected by ELISA assay. The supernatants were also assayed by TF-1assay for function. The results of this experiment are shown in FIG. 30.

Example 7

TF-1 proliferation assay and TF-1 functional fEPO assays are shown inFIGS. 11-24. TF-1 cells were seeded at 150,000 cells/ml in a T-75 flaskin growth medium overnight and on the day of the assay, cells wereseeded at 20,000 cells/well in 50 μl of assay medium (FIG. 11). TF-1cells were purchased from ATCC and the cell line was established fromthe bone marrow cells of a patient with erythroleukemia. The cell lineshows growth dependency with IL-1, GMesf, EPO and fEPO. Activity ismeasured by proliferation of TF-1 cells in response to fEPO. The extentof proliferation is measured by VAST-8. Cleavage of tetrazolium saltwst-8 to formazan by cellular mitochondrial dehydogenase is directlyproportional to the number of living cells. The formazan dye produced byviable cells is quantified by measuring the absorbance of the dyesolution at 450 nm (FIG. 13, FIG. 16, FIG. 19, FIG. 20, FIG. 21). InFIG. 13, the conditions were TF-1 cells seeded at varying densities of40,000; 30,000; 20,000; and 10,000 cells per well. Two differentincubation times, 48 hours and 72 hours, were used, as well as twodifferent fEPO concentrations (2500 ng/mL and 500 ng/mL), two differentdilution schemes (3× and 2.5×), and 24 hour starved cells as well asun-starved cells were used. Results of these experiments and functionalassays are described and shown in the figures and figure descriptions.

Example 8

Purification of Wild-Type and Para-Acetylphenylalanine (pAF) Variants ofFeline Erythropoietin (fEPO), and Selective Conjugation of Poly(ethyleneglycol) to pAF Variants

Purification of fEPO and pAF variants involves concentration anddiafiltration, followed by three column chromatography steps:phenylboronate, anion exchange, and hydrophobic interaction. Prior toPEGylation, the purified material is concentrated and exchanged intoPEGylation buffer.

UF/DF: Cell culture supernatant was concentrated and exchanged in Xdiavolumes of 50 mM HEPES pH 8.5 prior to chromatography loading using aSlice 200 (Sartorius Stedim) system connected to a MasterFlex pump.

Phenylboronate (PB) Chromatography

Phenylboronate resin was performed in negative capture mode using ProSepPB column equilibrated in 50 mM HEPES, pH 8.5. Material was collected inthe flow-through wash (50 mM HEPES, pH 8.5). Impurities were removedwith step elutions in 50 mM HEPES, 50 mM sorbitol pH 8.5; 50 mM Tris, 6M urea, pH 8.5; and 100 mM acetic acid.

Material from the PB flow-through was exchanged into 20 mM Tris pH 8.0by UF/DF into 20 mM Tris pH 8.0 as described above prior to loading ontoanion exchange chromatography.

Anion Exchange Chromatography (AEX)

Material was purified using a Q Sepharose High Performance column in anXK 16 column (GE Healthcare, Piscataway, N.J.), flow rate 120 cm/h.Material was loaded onto a column equilibrated in 20 mM Tris pH 8.0Elution was conducted using a linear AB gradient, where Buffer A=20 MMTris pH 8.0, Buffer B=20 mM Tris, 500 mM NaCl pH 8.0. Fixed-volumefractions were collected and analyzed by SDS-PAGE and anti-EPO ELISA.

Hydrophobic Interaction Chromatography (HIC)

AEX pool containing fEPO was diluted in 3.5 M ammonium sulfate to obtaina final 1.5 M ammonium sulfate concentration. Material was loaded onto aPhenyl Sepharose High Performance resin, 120 cm/h, equilibrated in 20 mMTris, 1.5 M ammonium sulfate pH 8.0. Elution was performed over a 20 CVlinear AB gradient, where A=20 mM Tris, 1.5 M ammonium sulfate pH 8.0and B=20 mM Tris, 50% (v/v) ethylene glycol, pH 8.0. Fixed-volumefractions were collected and analyzed by SDS-PAGE and anti-EPO ELISA.

PEGylation of fEPO pAF Variants

Relevant fractions were pooled and concentrated to ˜5 mg/ml with aVivaSpin column 10 000 MWCO@15000×g, 10 min per spin. Sample wasexchanged into 20 mM sodium acetate, 1 mM EDTA, pH 4.0. PEGylation wascommenced using a 12:1 mol ratio of PEG:protein using 20 kD PEG-oxyamine(Sunbright ME200-CA), and 1% (w/v) acethydrazide adjusted to pH 4.0 withacetic acid. PEGylation was conducted at 28 C for >12 hours and analyzedby SDS-PAGE (FIG. 31, FIG. 32, and FIG. 33). Variant A1 was PEGylatedwith a 30 kDa PEG, variant Y49 was PEGylated with a 40 kDa PEG, variantR53 was PEGylated with a 20 kDa PEG, variant D55 was PEGylated with a 30kDa PEG, variant P129 was PEGylated with a 30 kDa PEG.

Example 9

This example details introduction of a carbonyl-containing amino acidand subsequent reaction with an aminooxy-containing PEG.

This example demonstrates a method for the generation of a fEPOpolypeptide that incorporates a ketone-containing non-naturally encodedamino acid that is subsequently reacted with an aminooxy-containing PEGof approximately 5,000 MW. Each of the residues 21, 24, 38, 83, 85, 86,89, 116, 119, 121, 124, 125, 126, 127, and 128 is separately substitutedwith a non-naturally encoded amino acid having the following structure:

The sequences utilized for site-specific incorporation ofp-acetyl-phenylalanine into fEPO are disclosed in Table 2, and sequences(e.g. muttRNA and TyrRS LW1, 5, or 6) described above.

Once modified, the fEPO variant comprising the carbonyl-containing aminoacid is reacted with an aminooxy-containing PEG derivative of the form:

R-PEG(N)—O—(CH₂)_(n)—O—NH₂

where R is methyl, n is 3 and N is approximately 5,000 MW. The purifiedfEPO containing p-acetylphenylalanine dissolved at 10 mg/mL in 25 mM MES(Sigma Chemical, St. Louis, Mo.) pH 6.0, 25 mM Hepes (Sigma Chemical,St. Louis, Mo.) pH 7.0, or in 10 mM Sodium Acetate (Sigma Chemical, St.Louis, Mo.) pH 4.5, is reacted with a 10 to 100-fold excess ofaminooxy-containing PEG, and then stirred for 10-16 hours at roomtemperature (Jencks, W. J. Am. Chem. Soc. 1959, 81, pp 475). ThePEG-fEPO is then diluted into appropriate buffer for immediatepurification and analysis.

Example 10

Conjugation with a PEG consisting of a hydroxylamine group linked to thePEG via an amide linkage.

A PEG reagent having the following structure is coupled to aketone-containing non-naturally encoded amino acid using the proceduredescribed in the above examples:

R-PEG(N)—O—(CH₂)₂—NH—C(O)(CH₂)_(n)—O—NH₂

where R=methyl, n=4 and N is approximately 20,000 MW. The reaction,purification, and analysis conditions are as described in the aboveexamples.

Example 11

This example details the introduction of two distinct non-naturallyencoded amino acids into fEPO

This example demonstrates a method for the generation of a fEPOpolypeptide that incorporates non-naturally encoded amino acidcomprising a ketone functionality at two positions among the followingresidues: N24X* and G113X*; N38X* and Q115X*; N36X* and S85X*; N36X* andA125X*; N36X* and A128X*; Q86X* and S126X* wherein X* represents anon-naturally encoded amino acid. The fEPO polypeptide is prepared asdescribed in the above examples, except that the suppressor codon isintroduced at two distinct sites within the nucleic acid.

Example 12

This example details conjugation of fEPO polypeptide to ahydrazide-containing PEG and subsequent in situ reduction

A fEPO polypeptide incorporating a carbonyl-containing amino acid isprepared according to the procedure described in the above examples.Once modified, a hydrazide-containing PEG having the following structureis conjugated to the fEPO polypeptide:

R-PEG(N)—O—(CH₂)₂—NH—C(O)(CH₂)_(n)—X—NH—NH₂

where R=methyl, n=2 and N=10,000 MW and X is a carbonyl (C═O) group. Thepurified fEPO containing p-acetylphenylalanine is dissolved at between0.1-10 mg/mL in 25 mM MES (Sigma Chemical, St. Louis, Mo.) pH 6.0, 25 mMHopes (Sigma Chemical, St. Louis, Mo.) pH 7.0, or in 10 mM SodiumAcetate (Sigma Chemical, St. Louis, Mo.) pH 4.5, isreacted with a 10 to100-fold excess of aminooxy-containing PEG, and the correspondinghydrazone is reduced in situ by addition of stock 1M NaCNBH₃ (SigmaChemical, St. Louis, Mo.), dissolved in H₂O, to a final concentration of10-50 mM. Reactions are carried out in the dark at 4° C. to RT for 18-24hours. Reactions are stopped by addition of 1 M Tris (Sigma Chemical,St. Louis, Mo.) at about pH 7.6 to a final Tris concentration of 50 mMor diluted into appropriate buffer for immediate purification.

Example 13

This example details introduction of an alkyne-containing amino acidinto fEPO and derivatization with mPEG-azide.

The following residues, 21, 24, 38, 83, 85, 86, 89, 116, 119, 121, 124,125, 126, 127, and 128, are each substituted with the followingnon-naturally encoded amino acid:

The sequences utilized for site-specific incorporation ofp-propargyl-tyrosine into fEPO are muttRNA, et. al, that are describedin the above examples. The fEPO polypeptide containing the propargyltyrosine is expressed in E. coli and purified using the conditionsdescribed above.

The purified fEPO containing propargyl-tyrosine dissolved at between0.1-10 mg/mL in PB buffer (100 mM sodium phosphate, 0.15 M NaCl, pH=8)and a 10 to 1000-fold excess of an azide-containing PEG is added to thereaction mixture. A catalytic amount of CuSO₄ and Cu wire are then addedto the reaction mixture. After the mixture is incubated (including butnot limited to, about 4 hours at room temperature or 37° C., orovernight at 4° C.), H₂O is added and the mixture is filtered through adialysis membrane. The sample can be analyzed for the addition,including but not limited to, by similar procedures described in theabove examples.

In this Example, the PEG will have the following structure:

R-PEG(N)—O—(CH₂)₂—NH—C(O)(CH₂)_(n)—N₃

where R is methyl, n is 4 and N is 10,000 MW.

Example 14

This example details substitution of a large, hydrophobic amino acid infEPO with propargyl tyrosine.

A Phe, Trp or Tyr residue present within one the following regions offEPO: 1-7 (N-terminus), 27-38 (region between A helix and B helix),39-41 (Beta sheet 1), 42-46 (region between Beta sheet 1 and mini helixB'), 47-52 (mini B' helix), 53-54 (region between mini B′ helix and Bhelix), 84-89 (region between B helix and C helix), 114-121 (mini C′helix), 122-132 (region between mini C′ helix and Beta sheet 2), 133-135(Beta sheet 2), 136-137 (region between Beta sheet 2 and D helix),162-166 (C-terminus, is substituted with the following non-naturallyencoded amino acid as described in the above examples:

Once modified, a PEG is attached to the fEPO variant comprising thealkyne-containing amino acid. The PEG will have the following structure:

Me-PEG(N)—O—(CH₂)₂—N₃

and coupling procedures would follow those described in the aboveexamples. This will generate a fEPO variant comprising a non-naturallyencoded amino acid that is approximately isosteric with one of thenaturally-occurring, large hydrophobic amino acids and which is modifiedwith a PEG derivative at a distinct site within the polyp eptide.

Example 15

This example details generation of a fEPO homodimer, heterodimer,homomultimer, or heteromultimer separated by one or more PEG linkers.

The alkyne-containing fEPO variant described in the above examples isreacted with a bifunctional PEG derivative of the form:

N₃—(CH₂)_(n)—C(O)—NH—(CH₂)₂—O-PEG(N)—O—(CH₂)₂—NH—C(O)—(CH₂)_(n)—N₃

where n is 4 and the PEG has an average MW of approximately 5,000, togenerate the corresponding fEPO homodimer where the two fEPO moleculesare physically separated by PEG. In an analogous manner a fEPOpolypeptide may be coupled to one or more other polypeptides to formheterodimers, homomultimers, or heteromultimers. Coupling, purification,and analyses will be performed as described in the above examples.

Example 16

This example details coupling of a saecharide moiety to fEPO.

One residue of the following is substituted with the non-natural encodedamino acid below: 21, 24, 28, 30, 31, 36, 37, 38, 55, 72, 83, 85, 86,87, 89, 113, 116, 119, 120, 121, 123, 124, 125, 126, 127, 128, 129, 130,and 162 as described in the above examples.

Once modified, the fEPO variant comprising the carbonyl-containing aminoacid is reacted with a β-linked aminooxy analogue of N-acetylglucosamine(GlcNAc). The fEPO variant (10 mg/mL) and the aminooxy saccharide (21mM) are mixed in aqueous 100 mM sodium acetate buffer (pH 5.5) andincubated at 37° C. for 7 to 26 hours. A second saccharide is coupled tothe first enzymatically by incubating the saccharide-conjugated fEPO (5mg/mL) with UDP-galactose (16 mM) and β-1,4-galacytosyltransferase (0.4units/mL) in 150 mM HEPES buffer (pH 7.4) for 48 hours at ambienttemperature (Schanbacher et al. J. Biol. Chem. 1970, 245, 5057-5061).

Example 17

This example details generation of a PEGylated fEPO antagonist.

One of the following residues, 21, 24, 28, 30, 31, 36, 37, 38, 55, 72,83, 85, 86, 87, 89, 113, 116, 119, 120, 121, 123, 124, 125, 126, 127,128, 129, 130, and 162, is substituted with the following non-naturallyencoded amino acid as described in the above examples.

Once modified, the fEPO variant comprising the carbonyl-containing aminoacid will be reacted with an aminooxy-containing PEG derivative of theform:

R-PEG(N)—O—(CH₂)_(n)—O—NH₂

where R is methyl, n is 4 and N is 20,000 MW to generate a fEPOantagonist comprising a non-naturally encoded amino acid that ismodified with a PEG derivative at a single site within the polypeptide.Coupling, purification, and analyses is performed as described in theabove examples.

Example 18

Generation of a fEPO Homodimer, Heterodimer, Homomultimer, orHeteromultimer in Which the fEPO Molecules are Linked Directly

A fEPO variant comprising the alkyne-containing amino acid can bedirectly coupled to another fEPO variant comprising the azido-containingamino acid, each of which comprise non-naturally encoded amino acidsubstitutions at the sites described in the above examples. This willgenerate the corresponding fEPO homodimer where the two fEPO variantsare physically joined at the site 2 binding interface. In an analogousmanner a fEPO polypeptide may be coupled to one or more otherpolypeptides to form heterodimers, homomultimers, or heteromultimers.Coupling, purification, and analyses is performed as described in theabove examples.

Example 19 PEG-OH+Br—(CH₂)_(n)—C:CR′→PEG-O—(CH₂)_(n)—C≡CR′ A B

The polyalkylene glycol (P—OH) is reacted with the alkyl halide (A) toform the ether (B). In these compounds, n is an integer from one to nineand R′ can be a straight- or branched-chain, saturated or unsaturatedC1, to C20 alkyl or heteroalkyl group. R′ can also be a C3 to C7saturated or unsaturated cyclic alkyl or cyclic heteroalkyl, asubstituted or unsubstituted aryl or heteroaryl group, or a substitutedor unsubstituted alkaryl (the alkyl is a C1 to C20 saturated orunsaturated alkyl) or heteroalkaryl group. Typically, P—OH ispolyethylene glycol (PEG) or monomethoxy polyethylene glycol (mPEG)having a molecular weight of 800 to 40,000 Daltons (Da).

Example 20 mPEG-OH+Br—CH₂—C≡CH→mPEG-O—CH₂—C≡CH

mPEG-OH with a molecular weight of 20,000 Da (mPEG-OH 20 kDa; 2.0 g, 0.1mmol, Sunbio) was treated with NaH (12 mg, 0.5 mmol) in THF (35 mL). Asolution of propargyl bromide, dissolved as an 80% weight solution inxylene (0.56 mL, 5 mmol, 50 equiv., Aldrich), and a catalytic amount ofKI were then added to the solution and the resulting mixture was heatedto reflux for 2 h. Water (1 mL) was then added and the solvent wasremoved under vacuum. To the residue was added CH₂Cl₂ (25 mL) and theorganic layer was separated, dried over anhydrous Na₂SO₄, and the volumewas reduced to approximately 2 mL. This CH₂Cl₂ solution was added todiethyl ether (150 mL) drop-wise. The resulting precipitate wascollected, washed with several portions of cold diethyl ether, and driedto afford propargyl-O-PEG.

Example 21 mPEG-OH+Br—(CH₂)₃—C≡CH→mPEG-O—(CH₂)₃—C≡CH

The mPEG-OH with a molecular weight of 20,000 Da (mPEG-OH 20 kDa; 2.0 g,0.1 mmol, Sunbio) was treated with NaH (12 mg, 0.5 mmol) in THF (35 mL)Fifty equivalents of 5-chloro-1-pentyne (0.53 mL, 5 mmol, Aldrich) and acatalytic amount of KI were then added to the mixture. The resultingmixture was heated to reflux for 16 hours. Water (1 mL) was then addedand the solvent was removed under vacuum. To the residue was addedCH₂Cl₂ (25 mL) and the organic layer was separated, dried over anhydrousNa₂SO₄, and the volume was reduced to approximately 2 mL. This CH₂Cl₂solution was added to diethyl ether (150 mL) drop-wise. The resultingprecipitate was collected, washed with several portions of cold diethylether, and dried to afford the corresponding alkyne.

Example 22 (1) m-HOCH₂C₆H₄OH+NaOH+Br—CH₂—C≡CH→m-HOCH₂C₆H₄O—CH₂—C≡CH (2)m-HOCH₂C₆H₄O—CH₂—C≡CH+MsCl+N(Et)₃→m-MsOCH₂C₆H₄O—CH₂—C≡CH (3)m-MsOCH₂C₆H₄O—CH₂—C≡CH+LiBr→m-Br—CH₂C₆H₄O—CH₂—C≡CH (4)mPEG-OH+m-Br—CH₂C₆H₄O—CH₂—C≡CH→mPEG-O—CH₂—C₆H₄O—CH₂—C≡CH

To a solution of 3-hydroxybenzylalcohol (2.4 g, 20 mmol) in THF (50 mL)and water (2.5 mL) was first added powdered sodium hydroxide (1.5 g,37.5 mmol) and then a solution of propargyl bromide, dissolved as an 80%weight solution in xylene (3.36 mL, 30 mmol). The reaction mixture washeated at reflux for 6 hours. To the mixture was added 10% citric acid(2.5 mL) and the solvent was removed under vacuum. The residue wasextracted with ethyl acetate (3×15 mL) and the combined organic layerswere washed with saturated NaCl solution (10 mL), dried over MgSO4 andconcentrated to give the 3-propargyloxybenzyl alcohol.

Methanesulfonyl chloride (2.5 g, 15.7 mmol) and triethylamine (2.8 mL,20 mmol) were added to a solution of compound 3 (2.0 g, 11.0 mmol) inCH₂Cl₂ at 0° C. and the reaction was placed in the refrigerator for 16hours. A usual work-up afforded the mesylate as a pale yellow oil. Thisoil (2.4 g, 9.2 mmol) was dissolved in THF (20 mL) and LiBr (2.0 g, 23.0mmol) was added. The reaction mixture was heated to reflux for 1 hourand was then cooled to room temperature. To the mixture was added water(2.5 mL) and the solvent was removed under vacuum. The residue wasextracted with ethyl acetate (3×15 mL) and the combined organic layerswere washed with saturated NaCl solution (10 mL), dried over anhydrousNa₂SO₄, and concentrated to give the desired bromide.

mPEG-OH 20 kDa (1.0 g, 0.05 mmol, Sunbio) was dissolved in THF (20 mL)and the solution was cooled in an ice bath. NaH (6 mg, 0.25 mmol) wasadded with vigorous stirring over a period of several minutes followedby addition of the bromide obtained from above (2.55 g, 11.4 mmol) and acatalytic amount of KI. The cooling bath was removed and the resultingmixture was heated to reflux for 12 hours. Water (1.0) was added to themixture and the solvent was removed under vacuum. To the residue wasadded CH₂Cl₂ (25 mL) and the organic layer was separated, dried overanhydrous Na₂SO₄, and the volume was reduced to approximately 2 mL.Dropwise addition to an ether solution (150 mL) resulted in a whiteprecipitate, which was collected to yield the PEG derivative.

Example 23 mPEG-NH₂+X—C(O)—(CH₂)_(n)—C≡CR′→mPEG-NH—C(O)—(CH₂)_(n)—C≡CR′

The terminal alkyne-containing poly(ethylene glycol) polymers can alsobe obtained by coupling a poly(ethylene glycol) polymer containing aterminal functional group to a reactive molecule containing the alkynefunctionality as shown above.

Example 24 (1) HO₂C—(CH₂)₂—C≡CH+NHS+DCC→NHSO—C(O)—(CH₂)₂—C≡CH (2)mPEG-NH₂+NHSO—C(O)—(CH₂)₂—C≡CH→mPEG-NH—C(O)—(CH₂)₂—C≡H

4-pentynoic acid (2.943 g, 3.0 mmol) was dissolved in CH2C12 (25 mL).N-hydroxysuccinimide (3.80 g, 3.3 mmol) and DCC (4.66 g, 3.0 mmol) wereadded and the solution was stirred overnight at room temperature. Theresulting crude NHS ester 7 was used in the following reaction withoutfurther purification.

mPEG-NH₂ with a molecular weight of 5,000 Da (mPEG-NH₂, 1 g, Sunbio) wasdissolved in THF (50 mL) and the mixture was cooled to 4° C. NHS ester 7(400 mg, 0.4 mmol) was added portion-wise with vigorous stirring. Themixture was allowed to stir for 3 hours while warming to roomtemperature. Water (2 mL) was then added and the solvent was removedunder vacuum. To the residue was added CH₂Cl₂ (50 mL) and the organiclayer was separated, dried over anhydrous Na₂SO₄, and the volume wasreduced to approximately 2 mL. This CH₂Cl₂ solution was added to ether(150 mL) drop-wise. The resulting precipitate was collected and dried invacuo.

Example 25

This example represents the preparation of the methane sulfonyl ester ofpoly(ethylene glycol), which can also be referred to as themethanesulfonate or mesylate of poly(ethylene glycol). The correspondingtosylate and the halides can be prepared by similar procedures.

mPEG-OH+CH₃SO₂Cl+N(Et)₃→mPEG-O—SO₂CH₃→mPEG-N₃

The mPEG-OH (MW=3,400, 25 g, 10 mmol) in 150 mL of toluene wasazeotropically distilled for 2 hours under nitrogen and the solution wascooled to room temperature. To the solution was added 40 mL of dryCH₂Cl₂ and 2.1 mL of dry triethylamine (15 mmol). The solution wascooled in an ice bath and 12 mL of distilled methanesulfonyl chloride(15 mmol) was added dropwise. The solution was stirred at roomtemperature under nitrogen overnight and the reaction was quenched byadding 2 mL of absolute ethanol. The mixture was evaporated under vacuumto remove solvents, primarily those other than toluene, filtered,concentrated again under vacuum, and then precipitated into 100 mL ofdiethyl ether. The filtrate was washed with several portions of colddiethyl ether and dried in vacuo to afford the mesylate.

The mesylate (20 g, 8 mmol) was dissolved in 75 ml of THF and thesolution was cooled to 4° C. To the cooled solution was added sodiumazide (1.56 g, 24 mmol). The reaction was heated to reflux undernitrogen for 2 hours. The solvents were then evaporated and the residuediluted with CH₂Cl₂ (50 mL) The organic fraction was washed with NaClsolution and dried over anhydrous MgSO₄. The volume was reduced to 20 mland the product was precipitated by addition to 150 ml of cold dryether.

Example 26 (1) N₃—C₆H₄—CO₂H→N₃—C₆H₄CH₂OH (2) N₃—C₆H₄CH₂OH→Br—CH₂—C₆H₄—N₃(3) mPEG-OH+Br—CH₂—C₆H₄—N₃→mPEG-O—CH₂—C₆H₄—N₃

4-azidobenzyl alcohol can be produced using the method described in U.S.Pat. No. 5,998,595. Methanesulfonyl chloride (2.5 g, 15.7 mmol) andtriethylamine (2.8 mL, 20 mmol) were added to a solution of4-azidobenzyl alcohol (1.75 g, 11.0 mmol) in CH₂Cl₂ at 0° C. and thereaction was placed in the refrigerator for 16 hours. A usual work-upafforded the mesylate as a pale yellow oil. This oil (9.2 mmol) wasdissolved in THF (20 mL) and LiBr (2.0 g, 23.0 mmol) was added. Thereaction mixture was heated to reflux for 1 hour and was then cooled toroom temperature. To the mixture was added water (2.5 mL) and thesolvent was removed under vacuum. The residue was extracted with ethylacetate (3×15 mL) and the combined organic layers were washed withsaturated NaCl solution (10 mL), dried over anhydrous Na₂SO₄, andconcentrated to give the desired bromide.

mPEG-OH 20 kDa (2.0 g, 0.1 mmol, Sunbio) was treated with NaH (12 mg,0.5 mmol) in THF (35 mL) and the bromide (3.32 g, 15 mmol) was added tothe mixture along with a catalytic amount of KI. The resulting mixturewas heated to reflux for 12 hours. Water (1.0) was added to the mixtureand the solvent was removed under vacuum. To the residue was addedCH₂Cl₂ (25 mL) and the organic layer was separated, dried over anhydrousNa₂SO₄, and the volume was reduced to approximately 2 mL. Dropwiseaddition to an ether solution (150 mL) resulted in a precipitate, whichwas collected to yield mPEG-O—CH₂—C₆H₄—N₃.

Example 27NH₂-PEG-O—CH₂CH₂CO₂H+N₃—CH₂CH₂CO₂—NHS→N₃—CH₂CH₂—C(O)NH-PEG-O—CH₂CH₂CO₂H

NH₂-PEG-O—CH₂CH₂CO₂H (MW 3,400 Da, 2.0 g) was dissolved in a saturatedaqueous solution of NaHCO₃ (10 mL) and the solution was cooled to 0° C.3-azido-1-N-hydroxysuccinimdo propionate (5 equiv.) was added withvigorous stirring. After 3 hours, 20 mL of H₂O was added and the mixturewas stirred for an additional 45 minutes at room temperature. The pH wasadjusted to 3 with 0.5 N H₂SO₄ and NaCl was added to a concentration ofapproximately 15 wt %. The reaction mixture was extracted with CH₂Cl₂(100 mL×3), dried over Na₂SO₄ and concentrated. After precipitation withcold diethyl ether, the product was collected by filtration and driedunder vacuum to yield the omega-carboxy-azide PEG derivative.

Example 28 mPEG-OMs+HC≡CLi→mPEG-O—CH₂—CH₂—C≡C—H

To a solution of lithium acetylide (4 equiv.), prepared as known in theart and cooled to −78° C. in THF, is added dropwise a solution ofmPEG-OMs dissolved in THF with vigorous stirring. After 3 hours, thereaction is permitted to warm to room temperature and quenched with theaddition of 1 mL of butanol. 20 mL of H₂O is then added and the mixturewas stirred for an additional 45 minutes at room temperature. The pH wasadjusted to 3 with 0.5 N H₂SO₄ and NaCl was added to a concentration ofapproximately 15 wt %. The reaction mixture was extracted with CH₂Cl₂(100 mL×3), dried over Na₂SO₄ and concentrated. After precipitation withcold diethyl ether, the product was collected by filtration and driedunder vacuum to yield the omega-carboxy-azide PEG derivative.

Example 29

The azide- and acetylene-containing amino acids were incorporatedsite-selectively into proteins using the methods described in L. Wang,et al., (2001), Science 292:498-500, J. W. Chin et al., Science301:964-7 (2003)), J. W. Chin et al., (2002), Journal of the AmericanChemical Society 124:9026-9027; J. W. Chin, & P. G. Schultz, (2002),ChemBioChem 11:1135-1137; J. W. Chin, et al., (2002), PNAS United Statesof America 99:11020-11024: and, L. Wang, & P. G. Schultz, (2002), Chem.Comm., 1-10. Once the amino acids were incorporated, the cycloadditionreact was carried out with 0.01 mM protein in phosphate buffer (PB), pH8, in the presence of 2 naM PEG derivative, 1 mM CuSO₄, and ˜1 mgCu-wire for 4 hours at 37° C.

Example 30

In Vitro and In Vivo Activity of PEGylated fEPO Determined by theNormocythaemic Mouse Assay

PEG-fEPO, unmodified fEPO and buffer solution are administered to mice.The results will show superior activity and prolonged half life of thePEGylated fEPO of the present invention compared to unmodified fEPOwhich is indicated by significantly increased amounts of reticulocytesand a shift of reticulocyte count maximum using the same dose per mouse,

The normocythaemic mouse bioassay is known in the art (Pharm. EuropaSpec. Issue Erythropoietin BRP Bio 1997(2)). The samples are dilutedwith BSA-PBS. Normal healthy mice, 7-15 weeks old, are administered s.c.0.2 ml of PEGylated fEPO of the present invention. Over a period of 4days starting 72 hours after the administration, blood is drawn bypuncture of the tail vein and diluted such that 1 μl of blood waspresent in 1 ml of an 0.15 mot acridine orange staining solution. Thestaining time is 3 to 10 minutes. The reticulocyte counts are carriedout microfluorometrically in a flow cytometer by analysis of the redfluorescence histogram (per 30,000 blood cells analyzed). Eachinvestigated group consists of 5 mice per day, and the mice are bledonly once.

Bioassay In addition, fEPO polypeptides of the present invention areevaluated with respect to in vitro biological activity using a fEPOreceptor binding assay and a cell proliferation assay in whichbioactivity is determined by Ba/F3-fEPOR cell proliferation. Theprotocol for each assay is described in Wrighton et al. (1997) NatureBiotechnology 15:1261-1265, and in U.S. Pat. Nos. 5,773,569 and5,830,851. EC₅₀ values for the fEPO polypeptides prepared according tothis invention are the concentration of compound required to produce 50%of the maximal activity obtained with recombinant erythropoietin.

Example 31

Clinical Trial of the Safety and/or Efficacy of PEGylated fEPOComprising a Non-naturally Encoded Amino Acid.

Objective To compare the safety and pharmacokinetics of subcutaneouslyadministered PEGylated recombinant feline EPO comprising a non-naturallyencoded amino acid with the commercially available hEPO product PROCRITor ARANESP.

Patients Eighteen healthy cats of similar profile (age and weight) areenrolled in this study. The subjects have no clinically significantabnormal laboratory values for hematology or serum chemistry, and anegative urine toxicology screen, HIV screen, and hepatitis B surfaceantigen. They should not have any evidence of the following:hypertension; a history of any primary hematologic disease; history ofsignificant hepatic, renal, cardiovascular, gastrointestinal,genitourinary, metabolic, neurologic disease; a history of anemia orseizure disorder; a known sensitivity to bacterial or mammalian-derivedproducts, PEG, or human serum albumin; habitual and heavy consumer tobeverages containing caffeine; participation in any other clinical trialor had blood transfused or donated within 30 days of study entry; hadexposure to hEPO or fEPO within three months of study entry; had anillness within seven days of study entry; and have significantabnormalities on the pre-study physical examination or the clinicallaboratory evaluations within 14 days of study entry. All subjects areevaluable for safety and all blood collections for pharmacokineticanalysis are collected as scheduled. All studies are performed withinstitutional ethics committee approval and patient consent.

Study Design This is a Phase I, single-center, open-label, randomized,two-period crossover study in healthy male volunteers. Eighteen subjectsare randomly assigned to one of two treatment sequence groups (ninesubjects/group). EPO is administered over two separate dosing periods asa bolus s.c. injection in the upper thigh using equivalent doses of thePEGylated fEPO comprising a non-naturally encoded amino acid and thecommercially available product chosen. The dose and frequency ofadministration of the commercially available product is as instructed inthe package label. Additional dosing, dosing frequency, or otherparameter as desired, using the commercially available products may beadded to the study by including additional groups of subjects. Eachdosing period is separated by a time period to be based off of the humantrial version (e.g. a 14-day washout period). Subjects are confined tothe study center at least 12 hours prior to and 72 hours followingdosing for each of the two dosing periods, but not between dosingperiods. Additional groups of subjects may be added if there are to beadditional dosing, frequency, or other parameter, to be tested for thePEGylated fEPO as well. Multiple formulations of EPO that are approvedfor use may be used in this study. Epoetin alfa marketed as PROCRIT®and/or darbepoitein marketed as ARANESP® are commercially available EPOproducts that have also been used therapeutically in animals. Theexperimental formulation of fEPO is the PEGylated fEPO comprising anon-naturally encoded amino acid.

Blood Sampling Serial blood is drawn by direct vein puncture before andafter administration of EPO. Venous blood samples (5 mL) fordetermination of serum erythropoietin concentrations are obtained atabout 30, 20, and 10 minutes prior to dosing (3 baseline samples) and atapproximately the following times after dosing: 30 minutes and at 1, 2,5, 8, 12, 15, 18, 24, 30, 36, 48, 60 and 72 hours. Each serum sample isdivided into two aliquots. All serum samples are stored at −20° C. Serumsamples are shipped on dry ice. Fasting clinical laboratory tests(hematology, serum chemistry, and urinalysis) are performed immediatelyprior to the initial dose on day 1, the morning of day 4, immediatelyprior to dosing on day 16, and the morning of day 19.

Bioanalytical Methods A radioimmunoassay (RIA) kit procedure (DiagnosticSystems Laboratory [DSL], Webster Tex.), is used for the determinationof serum erythropoietin concentrations. The commercially available RIAis a double-antibody, competitive method that uses a rabbit polyclonalantiserum to urinary erythropoietin as the primary antibody and an¹²⁵I-labeled urinary erythropoietin as the tracer. Epoetin alfa ordarbepoietin is substituted for urinary erythropoietin provided in theDSL kit, in standards and quality control samples. Standardconcentrations used in the assay are 7.8, 15.6, 31.3, 50, 62.5, 100, and125 mIU/mL. Sensitivity, defined as the mean back-fit value for thelowest standard giving acceptable precision, is 8.6 mIU/mL, and theassay range is extended to 2,000 mIU/mL through quality controldilutions.

Safety Determinations Vital signs are recorded immediately prior to eachdosing (Days 1 and 16), and at 6, 24, 48, and 72 hours after eachdosing. Safety determinations are based on the incidence and type ofadverse events and the changes in clinical laboratory tests frombaseline. In addition, changes from pre-study in vital signmeasurements, including blood pressure, and physical examination resultsare evaluated.

Data Analysis Post-dose serum concentration values are corrected forpre-dose baseline erythropoietin concentrations by subtracting from eachof the post-dose values the mean baseline erythropoietin concentrationdetermined from averaging the erythropoietin levels from the threesamples collected at 30, 20, and 10 minutes before dosing. Pre-doseserum erythropoietin concentrations are not included in the calculationof the mean value if they are below the quantification level of theassay. Pharmacokinetic parameters are determined from serumconcentration data corrected for baseline erythropoietin concentrations.Pharmacokinetic parameters are calculated by model independent methodson a Digital Equipment Corporation VAX 8600 computer system using thelatest version of the BIOAVL software. The following pharmacokineticsparameters are determined: peak serum concentration (C_(max)); time topeak serum concentration (t_(max)); area under the concentration-timecurve (AUC) from time zero to the last blood sampling time (AUC₀₋₇₂)calculated with the use of the linear trapezoidal rule; and terminalelimination half-life (t_(1/2)), computed from the elimination rateconstant. The elimination rate constant is estimated by linearregression of consecutive data points in the terminal linear region ofthe log-linear concentration-time plot. The mean, standard deviation(SD), and coefficient of variation (CV) of the pharmacokineticparameters are calculated for each treatment. The ratio of the parametermeans (preserved formulation/non-preserved formulation) is calculated.

Safety Results The incidence of adverse events is equally distributedacross the treatment groups. There are no clinically significant changesfrom baseline or pre-study clinical laboratory tests or blood pressures,and no notable changes from pre-study in physical examination resultsand vital sign measurements. The safety profiles for the two treatmentgroups should appeared similar.

Pharmacokinetic Results Mean serum erythropoietin concentration-timeprofiles (uncorrected for baseline erythropoietin levels) in all 18subjects after receiving a single dose of commercially available hEPO(PROCRIT® or ARANESP®) are compared to the PEGylated fEPO and/orresearch or commercial fEPOs which are available. The PEGylated fEPO forcomparison is one of the present invention, comprising a non-naturallyencoded amino acid at each time point measured. All subjects should havepre-dose baseline erythropoietin concentrations within the normalphysiologic range. Pharmacokinetic parameters are determined from serumdata corrected for pre-dose mean baseline erythropoietin concentrationsand the C_(max) and t_(max) are determined. The mean t_(max) for hEPO(PROCRIT®) is significantly shorter than the tmax for the PEGylated hEPOcomprising the non-naturally encoded amino acid. Terminal half-lifevalues are significantly shorter for hEPO (PROCRIT®) compared with theterminal half-life for the PEGylated fEPO comprising a non-naturallyencoded amino acid.

Although the present study is conducted in healthy subjects, similarabsorption characteristics and safety profiles would be anticipated inother patient populations; such as patients with cancer or chronic renalfailure, post injury with injury-induced anemia, pediatric renal failurepatients, patients in autologous predeposit programs, or patientsscheduled for elective surgery.

In conclusion, subcutaneously administered single doses of PEGylatedfEPO comprising non-naturally encoded amino acid are safe and welltolerated by healthy subjects. Based on a comparative incidence ofadverse events, clinical laboratory values, vital signs, and physicalexamination results, the safety profiles of research/commercial EPOs,hEPO (PROCRIT®) and PEGylated fEPO comprising non-naturally encodedamino acid are equivalent. The PEGylated fEPO comprising non-naturallyencoded amino acid potentially provides large clinical utility topatients and health care providers.

Example 32

In vivo Activity of PEGylated fEPO Variants

The impact of PEG on the duration of activity of a protein is at leastpartially dependent on the size and structure (linear vs. branched) ofthe PEG. The comparative ability of different PEG size variants of fFPOto increase hematocrits (Het) was evaluated in healthy cats.

Recombinant fEPO variants containing a p-aminophenylalanine (pAF)substitution at position Al were expressed in a Chinese hamster ovarycell expression system. The protein was PEGylated with either 20 kD, 30kD or 40 kD oxyamino PEG at the site of the non-native amino acidsubstitution. The PEGylated fEPO variants were formulated in aformulation buffer consisting of 20 mM NaPO4, 140 mM NaCl, 0.005%polysorbate-80 at pH 6.2.

Twenty-four cats healthy (12 male/12 female) weighing approximately 3-6kg were purchased from a Class A vendor and allowed to acclimate to thestudy facility, their diet and husbandry procedures. Baseline bloodsamples were collected on Days-14 and Day-7 prior to enrollment in thestudy. Cats were sedated with acepromazine and isoflurane to reduce thestress of collecting blood samples. Animals which were free of clinicalsigns of disease and which had Hct values within the normal referenceranges for healthy cats were selected for enrollment in the study.

Cats were assigned to one of four treatment groups using a randomizedblock design which equalized baseline hematocrits between treatments.

TABLE 5 Treatment Dose Regimen # of Animals 1) Formulation Buffer SIDX16 (3M/3F) 2) fEPO A1 pAF-20K PEG 8 μg/kg, SIDX1 6 (3M/3F) 3) fEPO A1pAF-30K PEG 8 μg/kg, SIDX1 6 (3M/3F) 4) fEPO A1 pAF-40K PEG 8 μg/kg,SIDX1 6 (3M/3F)

Animals were bled on Day 0 prior to treatment and weighed. Animals weretreated once with their assigned treatments by subcutaneous injection.

Additional blood samples were collected on Days 3, 7, 10, 14, 17, 21,24, 28, 31, 35, 38 and 42 post-treatment. Hematocrits were determinedfor each sample. Daily feed consumption was also measured and animalswere observed daily for any health issues.

The effects of the various treatments upon hematocrits and RBC arepresented in FIG. 36.

Significant increases in Het values relative to the buffer controls wereobserved with either the 20 kD or 30 kD PEGylated fEPO variants within 3days of dosing. Animals treated with the 40 kD PEG variant exhibitedsignificant increases relative to the buffer controls by approximately10 days post-treatment. Maximum Hct values were observed on Day 10 foranimals treated with the 20 kD PEG variant, Day 14 for the 30 kD PEGvariant and Day 17 for the 40 kD PEG variant. Hematocrits for animalstreated with either the 20 or 30 kD PEG variants were significantlygreater than the buffer controls through at least 28 days post-dosing.These results suggest administration of PEG fEPO once per month shouldbe adequate to support the maintenance of increased Hct levels. Therewere no adverse events observed during the course of the study.

Example 33

Efficacy of PEGylated fEPO Variants in Anemic Cats

The ability of PEGylated fEPO variants to restore normal red blood cell(RBC) numbers in cats with anemia can be evaluated in cats with stageIII or stage IV chronic kidney disease (CKD). Cats with this conditionexhibit moderate to severe non-regenerative anemia due to the loss ofparenchymal renal cells which are the primary source of endogenous fEPO.

To evaluate the ability of PEGylated fEPO to increase red blood cellnumbers in cats with CKD and anemia, 12 cats (6 males and 6 females)weighing approximately 3-6 kg with a clinical history of CKD andhematocrits <30% are acclimated to the study facility, their diet andhusbandry procedures. Hematocrits and RBC counts from blood samplescollected on Days-14 and Day-7 prior to enrollment in the study are usedas baseline controls for each animal.

Cats are assigned to one of three treatment groups using a randomizedblock design which equalizes baseline hematocrits and RBCs betweentreatments. Each treatment group contains four animals (2 males/2females). PEGylated fEPO is administered once via subcutaneous injectionat doses ranging from 2-8 □g/kg.

Additional blood samples are collected on Days 3, 7, 10, 14, 17, 21, 24,28 and 31 post-treatment. Hematocrits and RBC counts are determined foreach sample. Daily feed consumption is also measured and animals areobserved and scored daily for clinical signs of depression and/orlethargy to assess quality of life.

Efficacy is determined by comparing the post-treatment hematocrits andRBC counts with the baseline values obtained prior to administration ofthe protein. The protein is considered efficacious if the mean dailyhematocrit and RBC count values exhibit a statistically significantincrease relative to the baseline values or if the mean daily valuesincrease to within the normal reference range values for theseparameters at any point during the post-treatment period.

It is understood that the examples and embodiments described herein arefor illustrative purposes only and that various modifications or changesin light thereof will be suggested to persons skilled in the art and areto be included within the spirit and purview of this application andscope of the appended claims. All publications, patents, and patentapplications cited herein are hereby incorporated by reference in theirentirety for all purposes.

1. A feline erythropoietin (fEPO) polypeptide comprising a non-naturallyencoded amino acid.
 2. The fEPO polypeptide of claim 1, wherein the fEPOpolypeptide is linked to at least one additional fEPO polypeptide. 3.The fEPO polypeptide of claim 1, wherein the non-naturally encoded aminoacid is linked to a water soluble polymer.
 4. The fEPO polypeptide ofclaim 3, wherein the water soluble polymer comprises a poly(ethyleneglycol) moiety.
 5. The fEPO polypeptide of claim 4, wherein thepoly(ethylene glycol) molecule is a bifunctional polymer.
 6. The fEPOpolypeptide of claim 5, wherein the bifunctional polymer is linked to asecond polypeptide.
 7. The fEPO polypeptide of claim 6, wherein thesecond polypeptide is a non-fEPO polypeptide.
 8. The fEPO polypeptide ofclaim 4, comprising at least two amino acids linked to a water solublepolymer comprising a poly(ethylene glycol) moiety.
 9. The fEPOpolypeptide of claim 8, wherein at least one amino acid linked to saidwater soluble polymer is a non-naturally encoded amino acid.
 10. ThefEPO polypeptide of claim 4, wherein the non-naturally encoded aminoacid is substituted at a position selected from the group consisting ofresidues 1-7, 27-54, 84-89, 114-137, 162-166 from SEQ ID NO:
 2. 11. ThefEPO polypeptide of claim 4, wherein the non-naturally encoded aminoacid is substituted at a position selected from the group consisting ofresidues 1, 2, 3, 4, 5, 6, 8, 9, 17, 21, 24, 25, 26, 27, 28, 30, 31, 32,34, 35, 36, 37, 38, 39, 40, 43, 45, 47, 50, 51, 52, 53, 54, 55, 56, 57,58, 65, 68, 72, 76, 77, 78, 79, 80, 82, 83, 84, 85, 86, 87, 88, 89, 90,91, 92, 107, 110, 111, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122,123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 136, 154,157, 158, 159, 160, 162, 163, 164, 165 and 166 from SEQ ID NO:
 2. 12.The fEPO polypeptide of claim 11, wherein the non-naturally encodedamino acid is substituted at a position selected from the groupconsisting of residues 2, 4, 17, 21, 24, 27, 28, 30, 31, 32, 34, 36, 37,38, 40, 50, 53, 55, 58, 65, 68, 72, 76, 80, 82, 83, 85, 86, 87, 89, 113,115, 116, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130,131, 132, 134, 136, and 162, and a combination thereof from SEQ ID NO:2.
 13. The fEPO polypeptide of claim 11, wherein the non-naturallyencoded amino acid is substituted at a position selected from the groupconsisting of residues 21, 24, 28, 30, 31, 36, 37, 38, 55, 72, 83, 85,86, 87, 89, 113, 116, 119, 120, 121, 123, 124, 125, 126, 127, 128, 129,130, and 162, and a combination thereof from SEQ ID NO:
 2. 14. The fEPOpolypeptide of claim 11, wherein the non-naturally encoded amino acid issubstituted at a position selected from the group consisting of residues21, 24, 38, 83, 85, 86, 89, 116, 119, 121, 124, 125, 126, 127, and 128,and a combination thereof from SEQ ID NO:
 2. 15. The fEPO polypeptide ofclaim 4, wherein the non-naturally encoded amino acid is substituted ata position selected from the group consisting of 24, 36, 38, 58, 65, 83,86, 113, 115, 126, and a combination thereof, from SEQ ID NO:
 2. 16. ThefEPO polypeptide of claim 1, wherein the fEPO polypeptide comprises asubstitution, addition or deletion that increases affinity of the fEPOpolypeptide for an erythropoietin receptor.
 17. The fEPO polypeptide ofclaim 1, wherein the fEPO polypeptide comprises an amino acidsubstitution, addition or deletion that increases the stability orsolubility of the fEPO polypeptide.
 18. The fEPO polypeptide of claim16, comprising an amino acid substitution selected from the groupconsisting of but not limited to, S9A, F48S, Y49S, A50S, Q59A, A73G,G101A, T106A, L108A, T132A, R139A, K140A, R143A, S146A, N147A, R150A,and K154A and combination thereof in SEQ ID NO:
 2. 19. The fEPOpolypeptide of claim 1, wherein the non-naturally encoded amino acid isreactive toward a water soluble polymer that is otherwise unreactivetoward any of the 20 common amino acids.
 20. The fEPO polypeptide ofclaim 1, wherein the non-naturally encoded amino acid comprises acarbonyl group, an acetyl group, an aminooxy group, a hydrazine group, ahydrazide group, a semicarbazide group, an azide group, or an alkynegroup.
 21. The fEPO polypeptide of claim 20, wherein the non-naturallyencoded amino acid comprises a carbonyl group.
 22. The fEPO polypeptideof claim 21, wherein the non-naturally encoded amino acid has thestructure:

wherein n is 0-10; R₁ is an alkyl, aryl, substituted alkyl, orsubstituted aryl; R₂ is H, an alkyl, aryl, substituted alkyl, andsubstituted aryl; and R₃ is H, an amino acid, a polypeptide, or an aminoterminus modification group, and R₄ is H, an amino acid, a polypeptide,or a carboxy terminus modification group.
 23. The fEPO polypeptide ofclaim 20, wherein the non-naturally encoded amino acid comprises anaminooxy group.
 24. The fEPO polypeptide of claim 20, wherein thenon-naturally encoded amino acid comprises a hydrazide group.
 25. ThefEPO polypeptide of claim 20, wherein the non-naturally encoded aminoacid comprises a hydrazine group.
 26. The fEPO polypeptide of claim 20,wherein the non-naturally encoded amino acid residue comprises asemicarbazide group.
 27. The fEPO polypeptide of claim 20, wherein thenon-naturally encoded amino acid residue comprises an azide group. 28.The fEPO polypeptide of claim 27, wherein the non-naturally encodedamino acid has the structure:

wherein n is 0-10; R₁ is an alkyl, aryl, substituted alkyl, substitutedaryl or not present; X is 0, N, S or not present; m is 0-10; R₂ is H, anamino acid, a polypeptide, or an amino terminus modification group, andR₃ is H, an amino acid, a polypeptide, or a carboxy terminusmodification group.
 29. The fEPO polypeptide of claim 20, wherein thenon-naturally encoded amino acid comprises an alkyne group.
 30. The fEPOpolypeptide of claim 29, wherein the non-naturally encoded amino acidhas the structure:

wherein n is 0-10; R₁ is an alkyl, aryl, substituted alkyl, orsubstituted aryl; X is O, N, S or not present; m is 0-10, R₂ is H, anamino acid, a polypeptide, or an amino terminus modification group, andR₃ is H, an amino acid, a polypeptide, or a carboxy terminusmodification group.
 31. The fEPO polypeptide of claim 4, wherein thepoly(ethylene glycol) molecule has a molecular weight of between about 1and about 100 kDa.
 32. The fEPO polypeptide of claim 31, wherein thepoly(ethylene glycol) molecule has a molecular weight of between 1 kDaand 50 kDa.
 33. The fEPO polypeptide of claim 4, which is made byreacting a fEPO polypeptide comprising a carbonyl-containing amino acidwith a poly(ethylene glycol) molecule comprising an aminooxy, ahydroxylamine, hydrazine, hydrazide or semicarbazide group.
 34. The fEPOpolypeptide of claim 33, wherein the aminooxy, hydroxylamine, hydrazine,hydrazide or semicarbazide group is linked to the poly(ethylene glycol)molecule through an amide linkage.
 35. The fEPO polypeptide of claim 4,which is made by reacting a poly(ethylene glycol) molecule comprising acarbonyl group with a polypeptide comprising a non-naturally encodedamino acid that comprises an aminooxy, a hydroxylamine, hydrazide orsemicarbazide group.
 36. The fEPO polypeptide of claim 4, which is madeby reacting a fEPO polypeptide comprising an alkyne-containing aminoacid with a poly(ethylene glycol) molecule comprising an azide moiety.37. The fEPO polypeptide of claim 4, which is made by reacting a fEPOpolypeptide comprising an azide-containing amino acid with apoly(ethylene glycol) molecule comprising an alkyne moiety.
 38. The fEPOpolypeptide of claim 4, wherein the functional group of thenon-naturally encoded amino acid is linked to the poly(ethylene glycol)molecule through an amide linkage.
 39. The fEPO polypeptide of claim 4,wherein the poly(ethylene glycol) molecule is a branched or multiarmedpolymer.
 40. The fEPO polypeptide of claim 39, wherein each branch ofthe poly(ethylene glycol) branched polymer has a molecular weight ofbetween 5 kDa and 30 kDa.
 41. The fEPO polypeptide of claim 1, whereinthe polypeptide is an erythropoietin antagonist.
 42. The fEPOpolypeptide of claim 41, wherein the non-naturally encoded amino acid issubstituted at a position selected from the group consisting of residuesincluding, but not limited to, V11, R14, Y15, D96, K97, S100, R103,S104, T107, L108, and R110, and a combination thereof from SEQ ID NO: 2.43. The fEPO polypeptide of claim 41, wherein the non-naturally encodedamino acid is linked to a water soluble polymer.
 44. The fEPOpolypeptide of claim 41, wherein the water soluble polymer comprises apoly(ethylene glycol) moiety.
 45. The fEPO polypeptide according toclaim 41, wherein the non-naturally encoded amino acid linked to a watersoluble polymer is present within the Site II region of the fEPOpolypeptide.
 46. The fEPO polypeptide according to claim 41, wherein thenon-naturally encoded amino acid linked to a water soluble polymerprevents dimerization of the fEPO receptor by preventing the fEPOantagonist from binding to a second fEPO receptor.
 47. The fEPOpolypeptide according to claim 41, wherein an amino acid other thanleucine is substituted for L108 in SEQ ID NO:
 2. 48. The fEPOpolypeptide according to claim 47, wherein arginine is substituted forL108 in SEQ ID NO:
 2. 49. The fEPO polypeptide of claim 1, wherein thenon-naturally encoded amino acid comprises a saccharide moiety.
 50. ThefEPO polypeptide of claim 3, wherein the water soluble polymer is linkedto the polypeptide via a saccharide moiety.
 51. An isolated nucleic acidcomprising a polynucleotide that hybridizes under stringent conditionsto SEQ ID NO:24, SEQ ID NO:25, SEQ ID NO:26, or SEQ ID NO:27 wherein thepolynucleotide comprises at least one selector codon.
 52. The isolatednucleic acid of claim 51, wherein the selector codon is selected fromthe group consisting of an amber codon, ochre codon, opal codon, aunique codon, a rare codon, and a four-base codon.
 53. A method ofmaking the fEPO polypeptide of claim 4, the method comprising contactingan isolated fEPO polypeptide comprising a non-naturally encoded aminoacid with a water soluble polymer comprising a moiety that reacts withthe non-naturally encoded amino acid.
 54. The method of claim 53,wherein the water soluble polymer comprises a polyethylene glycolmoiety.
 55. The method of claim 53, wherein the non-naturally encodedamino acid residue comprises a carbonyl group, an aminooxy group, ahydrazide group, a semicarbazide group, an azide group, or an alkynegroup.
 56. The method of claim 55, wherein the non-naturally encodedamino acid residue comprises a carbonyl moiety and the water solublepolymer comprises an aminooxy, a hydroxylamine, hydrazide orsemicarbazide moiety.
 57. The method of claim 55, wherein thenon-naturally encoded amino acid residue comprises an alkyne moiety andthe water soluble polymer comprises an azide moiety.
 58. The method ofclaim 55, wherein the non-naturally encoded amino acid residue comprisesan azide moiety and the water soluble polymer comprises an alkynemoiety.
 59. The method of claim 54, wherein the polyethylene glycolmoiety has an average molecular weight of between about 1 and about 100kDa.
 60. The method of claim 58, wherein the polyethylene glycol moietyis a branched or multiarmed polymer.
 61. A composition comprising thefEPO polypeptide of claim 1 and a pharmaceutically acceptable carrier.62. The composition of claim 61, wherein the non-naturally encoded aminoacid is linked to a water soluble polymer.
 63. A method of treating apatient having a disorder modulated by fEPO comprising administering tothe patient a therapeutically-effective amount of the pharmaceuticalcomposition of claim
 61. 64. A cell comprising the nucleic acid of claim51.
 65. The cell of claim 64, wherein the cell comprises an orthogonaltRNA synthetase and an orthogonal tRNA.
 66. A method of making a fEPOpolypeptide comprising a non-naturally encoded amino acid, the methodcomprising, culturing cells comprising a polynucleotide orpolynucleotides encoding a fEPO polypeptide and comprising a selectorcodon, an orthogonal RNA synthetase and an orthogonal tRNA underconditions to permit expression of the fEPO polypeptide comprising anon-naturally encoded amino acid; and purifying the fEPO polypeptidefrom the cells.
 67. A method of increasing serum half-life orcirculation time of fEPO, the method comprising substituting anon-naturally encoded amino acid for any one or more amino acids innaturally occurring fEPO.
 68. A fEPO polypeptide encoded by apolynucleotide having a sequence shown in SEQ ID NO: 24; SEQ ID NO: 25;SEQ ID NO:26 or SEQ ID NO: 27, wherein at least one amino acid issubstituted by a non-naturally encoded amino acid.
 69. The fEPOpolypeptide of claim 68, wherein the non-naturally encoded amino acid islinked to a water soluble polymer.
 70. The fEPO polypeptide of claim 68,wherein the water soluble polymer comprises a poly(ethylene glycol)moiety.
 71. The fEPO polypeptide of claim 68, wherein the non-naturallyencoded amino acid is substituted at a position selected from the groupconsisting of residues 1, 2, 3, 4, 5, 6, 8, 9, 17, 21, 24, 25, 26, 27,28, 30, 31, 32, 34, 35, 36, 37, 38, 39, 40, 43, 45, 47, 50, 51, 52, 53,54, 55, 56, 57, 58, 68, 72, 76, 77, 78, 79, 80, 82, 83, 84, 85, 86, 87,88, 89, 90, 91, 92, 107, 110, 111, 113, 114, 115, 116, 117, 118, 119,120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133,134, 136, 154, 157, 158, 159, 160, 162, 163, 164, 165 and 166 from SEQID NO:
 3. 72. The fEPO polypeptide of claim 68, wherein thenon-naturally encoded amino acid comprises a carbonyl group, an aminooxygroup, a hydrazide group, a hydrazine group, a semicarbazide group, anazide group, or an alkyne group.
 73. The fEPO polypeptide of claim 70,wherein the poly(ethylene glycol) moiety has a molecular weight ofbetween about 1 and about 100 kDa.
 74. The fEPO polypeptide of claim 70,wherein the poly(ethylene glycol) moiety has a molecular weight ofbetween 5 kDa and 40 kDa.
 75. The fEPO polypeptide of claim 70, whereinthe polyethylene glycol moiety is a branched or multiarmed polymer. 76.A pharmaceutical composition comprising the fEPO polypeptide of claim 68and a pharmaceutically acceptable carrier.
 77. A non-humanerythropoietin polypeptide having an amino acid sequence selected fromthe group consisting of SEQ ID NO: 30; SEQ ID NO: 31; SEQ ID NO:32 andSEQ ID NO: 33, wherein said non-human erythropoietin polypeptidecomprises a non-naturally encoded amino acid substitution or addition.